Hemojuvelin fusion proteins and uses thereof

ABSTRACT

The present invention provides a hemojuvelin (HJV) fusion protein (e.g., a human HJV.Fc) protein, polynucleotides and vectors encoding such proteins, and methods for making such proteins. Also provided are methods for treating iron-related disorders which include administration of a HJV fusion protein to a patient in need thereof.

CROSS REFERENCED APPLICATIONS

This application is a national stage application under 35 U.S.C. 371 ofInternational Application No. PCT/US2008/059753, filed on Apr. 9, 2008,which claims benefit under 35 U.S.C. 119(e) of U.S. Provisional PatentApplication Ser. No. 60/922,459 filed on Apr. 9, 2007, the contents ofwhich are incorporated by reference in their entireties.

STATEMENT AS TO FEDERALLY FUNDED RESEARCH

This invention was made with the United States Government support underGrant numbers F32 DK-068997, RO1 DK-69533, RO1 DK-71837, T32 HL07623,K08 DK-075846, and RO1 DK-053813 awarded by National Institutes ofHealth (NIH). The Government of the United States has certain rights inthe invention.

FIELD OF THE INVENTION

The present invention is directed towards a soluble form of hemojuvelin(HJV), particularly HJV fusion proteins for the use in compositions andmethods for regulation of iron metabolism.

REFERENCE TO A “SEQUENCE LISTING”

The sequence listing material in the text file entitled“12595423_Seq_List_New.txt” (112,388 bytes), which was created on Jul.29, 2010, is herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

In general, the invention relates to hemojuvelin fusion proteins anduses of such proteins.

Iron homeostasis is vitally important. Iron is required for manybiological reactions and processes, including oxygen transport byhemoglobin, yet excessive iron can be toxic. To maintain proper serumlevels, a complex system of iron transport and storage involvingorganisms employ iron storage protein ferritin, the iron transportertransferrin, and the transferrin receptor. When feedback controllingthis system is disrupted, either insufficient iron (anemia) or ironoverload (hemochromatosis) can result. Mutations in HFE2, the genecoding for hemojuvelin, have been previously been identified to causeiron overload in chromosome 1q-linked juvenile hemochromatosis.

Hemojuvelin was identified as a member of the Repulsive GuidanceMolecule (RGM) family of proteins, which include DRAGON and RGMa. Theproteins were initially identified as being responsive to thetranscription factor DRG11 (see, e.g., U.S. Patent ApplicationPublication No. 2004/0014141, which is incorporated herein by reference)and their ability to promote neural adhesion and survival.

SUMMARY OF THE INVENTION

The present invention relates to methods and compositions comprising asoluble form of HJV. In some embodiments the soluble form of HJV is HJVfused to a stabilizing polypeptide, such as for example, but not limitedto fusion with a Fc polypeptide or fragment thereof.

As disclosed herein, the inventors have discovered a novel therapeutic,HJV.Fc, useful in the treatment of conditions involving hepcidinregulation (e.g., iron-related disorders such as those describedherein). HJV.Fc increases ferroportin expression, mobilizes splenic ironstores, and increases serum iron levels in vivo. The inventors also showherein that BMP-2 administration increases hepcidin expression anddecreases serum iron levels in vivo.

Accordingly, one aspect of the present invention provides HJV fusionproteins (for example, HJV.Fc), pharmaceutical compositions containingsuch proteins, polynucleotides encoding such proteins, and methods fortreating HJV-related disorders such as iron-related disorders includingiron overload and anemia of chronic disease (e.g., those describedherein). These data also support a role for modulators of the BMPsignaling pathway in treating diseases of iron overload and anemia ofchronic disease.

Accordingly, in a first aspect the invention provides a fusion proteinincluding a hemojuvelin (HJV) fragment or full length HJV protein, wherethe fragment has at least 85% (e.g., at least 90%, 95%, or 99%, or 100%)amino acid sequence identity to a functional portion of the HJV protein(e.g., the human HJV protein); and a first fusion partner, such as IgG1Fc, e.g., human or mouse IgG1 Fc, covalently bonded to the HJV fragment.The first fusion partner may be covalently bonded to the N-terminus orto the C-terminus of the HJV protein fragment. The HJV fragment may be asoluble fragment of the full length HJV, may lack the C-terminal GPIanchoring domain, or may lack the N-terminal signal sequence (e.g.,lacks both the C-terminal GPI anchoring domain and the N-terminal signalsequence). The HJV sequence may be based on any naturally occurring HJVisoform. The fusion protein may further include a second fusion partner(e.g., in place of the N-terminal signal sequence). The fusion proteinmay have an amino acid sequence with at least 85% (e.g., at least 90%,95% or 99%, or 100%) identity to the sequence of SEQ ID NO:1. The fusionprotein may have enhanced proteolytic stability (e.g., a mutation at aposition corresponding to amino acid 172 such as an aspartic acid toalanine point mutation of isoform A of the human HJV sequence). Thefusion protein with enhanced proteolytic stability may have an aminoacid sequence with at least 85% (e.g., at least 90%, 95%, or 99%)sequence identity to SEQ ID NO:7. The HJV fragment must be a functionalfragment. As used herein, the fragment must display at least 30% agonistor antagonist biological activity of the wild-type HJV as determined inany in vitro or in vivo test, such as the assays as used herein and inthe Examples. The biological activity in one embodiment is related toiron regulation. The fragment must be at least 6 amino acids, in anotherembodiment, the fragment must be at least 7 or at least 10, or at least14, or at least 18, or at least 25, or at least 30, or at least 50, orat least 70 amino acids, or more than 70 amino acids in length. Thefusion protein may be produced recombinantly, may be isolated, or may besubstantially pure.

In another aspect, the invention provides a pharmaceutical compositionincluding the fusion protein of the first aspect and a pharmaceuticallyacceptable carrier.

In another aspect, the invention also provides a method for producingthe fusion protein of the invention including introducing into a cellwith a vector including a sequence encoding the fusion protein operablylinked to a promoter; and culturing the cell under conditions where theprotein is expressed. The method may further include purifying theprotein.

The invention also provides a polynucleotide encoding the fusion proteinof the first aspect, a vector including the polynucleotide, and a hostcell containing the vector. The vector may be suitable for expressingthe fusion protein in a eukaryotic (e.g., mammalian, yeast, insect) cellor in prokaryotic cell (e.g., E. coli). The host cell may be any hostcell described herein.

The invention also features a method for treating a patient having ahepcidin- or an HJV-related disorder such as iron-related disorder. Themethod includes administering to the patient the fusion protein of thefirst aspect in an amount effective to treat the patient. Theiron-related disorder may be any of those described herein, e.g.,hereditary hemochromatosis, porphyria cutanea tarda, hereditaryspherocytosis, hyprochromic anemia, hysererythropoietic anemia (CDAI),faciogenital dysplasia (FGDY), Aarskog syndrome, atransferrinemia,sideroblastic anemia (SA), pyridoxine-responsive sidero-blastic anemia,and a hemoglobinopathy, thalassemia, sickle cell, anemia of chronicdisease, iron deficiency anemia, functional iron deficiency, ormicrocytic anemia. A “fusion protein” is meant a polypeptide sequenceformed from two or more (e.g., three, four, or five) heterologous joinedsequences. The HJV fusion protein may be administered by any route or anany dosage described herein.

Accordingly, one aspect of the present invention relates to a fusionprotein comprising: (a) a hemojuvelin (HJV) polypeptide or fragmentthereof, wherein the fragment has at least 95% amino acid sequenceidentity to a portion of the HJV protein and is at least 6 amino acids;and (b) a first fusion partner which is conjugated to said HJVpolypeptide or fragment thereof. In some embodiments, the first fusionpartner is fused to the N-terminus or to the C-terminus of the HJVprotein fragment. In some embodiments, the first fusion partner is IgG1Fc, such as human IgG1 Fc.

In some embodiments, a HJV fragment useful in the HJV fusion protein asdisclosed herein is a soluble fragment. In another embodiment, a HJVfragment is a functional HJV fragment. In some embodiments, a HJVfragment can lack the C-terminal GPI anchoring domain, or alternatively,a HJV fragment can lack the N-terminal signal sequence, oralternatively, a HJV fragment can lack both the C-terminal GPI anchoringdomain and the N-terminal signal sequence.

In some embodiments, a HJV fusion protein as disclosed herein canfurther comprise a second fusion partner. In some embodiments, the HJVprotein or fragment thereof is conjugated to the first fusion partner byway of a covalent bond, such as a peptide bond, although the HJV proteinand fusion partner can be conjugated together by any means commonlyknown by persons of ordinary skill in the art.

In some embodiments, a HJV fusion protein as disclosed herein comprisesa HJV fragment which lacks the N-terminal signal sequence. In someembodiments, the HJV protein useful in the HJV fusion protein asdisclosed herein is a human HJV protein, such as a human HJV proteinwhich corresponds to amino acid SEQ ID NO: 2, or 3 or 4, or functionalvariants or functional derivatives thereof, as those terms are definedherein. In alternative embodiments, a human HJV protein useful in theHJV fusion protein as disclosed herein is not SEQ ID NO: 62, 63 or 64(which refer to SEQ ID NOs 7, 10 and 30 of U.S. Pat. No. 7,319,138,respectively).

In some embodiments, a HJV protein useful in the HJV fusion protein asdisclosed herein has enhanced proteolytic stability, for example wherethe enhanced proteolytic stability is conferred by a sequence alterationat the amino acid corresponding to amino acid 172 of isoform A of humanHJV (SEQ ID NO: 2).

Further embodiments relate to a HJV fusion protein which comprises, oralternatively consists essentially of an amino acid sequence with atleast 95% identity to the sequence of SEQ ID NO: 10, or a functionalderivative or functional variant thereof. In another embodiment, a HJVfusion protein can have an amino acid sequence which comprises, oralternatively consists essentially of the sequence of SEQ ID NO: 10, ora functional derivative or functional variant thereof.

In an alternative embodiment, a HJV fusion protein can comprise an aminoacid sequence with at least 95% identity to the sequence of SEQ ID NO:7,or in a further embodiment, the HJV fusion protein can have an aminoacid sequence comprising, or alternatively consisting essentially of thesequence of SEQ ID NO:7.

In an alternative embodiment, a HJV fusion protein can comprise an aminoacid sequence with at least 95% identity to the sequence of SEQ ID NO:1.In another embodiment, the HJV fusion protein can have an amino acidsequence comprising, or alternatively consisting essentially of thesequence of SEQ ID NO:1.

Another aspect of the present invention relates to the use of the HJVfusion protein as disclosed herein for the treatment or prevention of aHJV-related disorder, such as for example an iron-related disorder. Ironrelated disorders are well known by persons of ordinary skill in theart, for example but are not limited to; hereditary hemochromatosis,porphyria cutanea tarda, hereditary spherocytosis, hyprochromic anemia,hysererythropoietic anemia (CDAI), faciogenital dysplasia (FGDY),Aarskog syndrome, atransferrinemia, sideroblastic anemia (SA),pyridoxine-responsive sidero-blastic anemia, and a hemoglobinopathy,thalassemia, sickle cell, anemia of chronic disease, iron deficiencyanemia, functional iron deficiency, and microcytic anemia.

Another aspect of the present invention relates to a pharmaceuticalcomposition comprising the HJV fusion protein as disclosed herein and apharmaceutically acceptable carrier.

Another aspect of the present invention relates to a method forproducing a HJV fusion protein as disclosed herein, comprising (a)introducing into a cell with a vector comprising a sequence encoding thefusion protein operably linked to a promoter; and (b) culturing the cellunder conditions where said protein is expressed. In some embodiments,the method for producing the HJV fusion protein as disclosed hereinfurther comprises a step of purifying the protein of step (b) by anymethod commonly known by one of ordinary skill in the art.

Another aspect of the present invention relates to a polynucleotideencoding the HJV fusion protein as disclosed herein, wherein thepolynucleotide encodes both a HJV polypeptide or fragment thereof whichhas at least 85% amino acid sequence identity to a portion of the HJVprotein; and a first fusion partner.

Another aspect of the present invention relates to a vector comprisingthe polynucleotide as discussed herein. In some embodiments, the vectoris a viral vector, such as for example but not limited to an adenoviralvector, a poxvirus vector and a lentiviral vector. In some embodiments,the vector can comprise a nucleic acid sequence which encodes a HJVpolypeptide or fragment thereof which has at least 95% amino acidsequence identity to a portion of the HJV protein; and a first fusionpartner, wherein the nucleic acid sequence is operatively linked totissue- or cell-type specific promoter, such as but no limited tomuscle- or liver specific promoters, such as those disclosed herein andother muscle and/or liver promoters which are commonly known by personsof ordinary skill in the art.

Another aspect of the present invention relates to a pharmaceuticalcomposition comprising a vector which comprises the nucleic acidencoding the HJV fusion protein as disclosed herein and, optionally, apharmaceutically acceptable carrier.

Another aspect of the present invention relates to a host cellcomprising the vector as disclosed herein, where the vector comprisesthe nucleic acid encoding the HJV fusion protein as disclosed herein.

Another aspect of the present invention relates to a method for treatingor preventing a patient having an HJV-related disorder comprisingadministering to a patient the HJV fusion protein as disclosed herein inan amount effective to treat said patient. In some embodiments, aHJV-related disorder which can be treated by the methods as disclosedherein is an iron-related disorder, such as but not limited to;hereditary hemochromatosis, porphyria cutanea tarda, hereditaryspherocytosis, hyprochromic anemia, hysererythropoietic anemia (CDAI),faciogenital dysplasia (FGDY), Aarskog syndrome, atransferrinemia,sideroblastic anemia (SA), pyridoxine-responsive sidero-blastic anemia,and a hemoglobinopathy, thalassemia, sickle cell, anemia of chronicdisease, iron deficiency anemia, functional iron deficiency, andmicrocytic anemia.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram depicting the role of hemojuvelin (HJV) inthe BMP signaling pathway and hepcidin regulation. HJV interacts withBMP ligands and BMP type I (R-I) and type II receptors (R-II) togenerate an active signaling complex. Upon formation of the complex,type II receptors phosphorylate type I receptors, which thenphosphorylate receptor-activated Smad1, Smad5, and Smad8 (R-Smad).Phosphorylated R-Smads form a complex with common mediator Smad4(Co-Smad), and the Smad complex translocates to the nucleus, where itincreases transcription of hepcidin mRNA.

FIGS. 2A and 2B show that hemojuvelin signals via the BMP, but not theTGF-β, pathway. HepG2 cells were transfected with a BMP-responsivefirefly luciferase reporter (a, BRE-Luc) or TGF-β-responsive fireflyluciferase reporter (b, CAGA-Luc) and a control Renilla luciferasevector (pRL-TK), without or with 2 ng-2 mg cDNA encoding mousehemojuvelin (Hjv). As negative and positive controls, cells without Hjvwere incubated in the absence (control) or presence of 50 ng ml⁻¹ BMP-2(FIG. 2A) or 1 ng ml⁻¹ TGF-β1 (FIG. 2B). Cells transfected with Hjv wereincubated in the absence of exogenous BMP-2 or TGF-β ligands. Celllysates were analyzed for luciferase activity. Relative luciferaseactivity was calculated as the ratio of firefly to Renilla luciferaseactivity, to control for transfection efficiency, and is expressed as amultiple of the activity of unstimulated cells transfected with reporteralone (control). Results are reported as the mean±s.d. n=2 to 4 in eachgroup. * P<0.05 (compared with control). Exact P-values are shown abovebars.

FIGS. 3A-3C show that hemojuvelin-mediated BMP signaling isligand-dependent. FIGS. 3A and 3B show HepG2 cells were transfected witha BMP-responsive firefly luciferase reporter (BRE-Luc) and a controlRenilla luciferase vector (pRL-TK) alone (bars 1-2, 5-6) or with 40ng/ml cDNA encoding murine hemojuvelin (Hjv) (bars 3-4). Transfectedcells were treated in the absence (bars 1-4) or presence of 25 ng/mlBMP-2 (bars 5-6) for 16 hours, without (bars 1, 3, 5) or with 1 μg/mlnoggin (FIG. 3A, bars 2, 4, 6) or 20 μg/ml neutralizing antibody againstBMP-2 and BMP-4 (FIG. 3B, αBMP2/4, bars 2, 4, 6) for 48 hours followedby measurement of luciferase activity. Relative luciferase activity wascalculated as the ratio of firefly to Renilla luciferase values tocontrol for transfection efficiency and is expressed as fold increasecompared with unstimulated cells transfected with reporter alone.Results are reported as the mean+/−standard deviation (n=2 to 6 in eachgroup; * P<0.05 for treatment with noggin or αBMP2/4 compared to notreatment in each group: a, bar 2 compared to 1 P=0.0009, bar 4 comparedto 3 P=0.03, bar 6 compared to 5 P=0.0006; b, bar 2 compared to 1P=0.003, bar 4 compared to 3 P=0.007, bar 6 compared to 5 P=0.00008).FIG. 3C shows results from reverse transcription PCR which was performedon total RNA from HepG2 cells using primers for BMP2 or BMP4 asindicated (lanes 3-4). Purified plasma cDNAs encoding BMP-2 or BMP-4were used as positive controls (+, lane 1), and reactions withouttemplate were used as negative controls (−, lane 2).

FIGS. 4A-4C show that HJV.Fc binds ¹²⁵I-BMP-2 and ¹²⁵I-BMP-4 insolution. FIG. 4A shows a Western blot of purified HJV.Fc fusion proteinwith a rabbit polyclonal antibody generated against a C-terminal peptideof hemojuvelin upstream (at amino acid 399) of its GPI anchor (α-HJV,left panel) or anti-human Fc antibody (α-Fc, right panel). Bands at ˜75kDa and ˜60 kDa correspond to the predicted size of the Fc portion ofhuman immunoglobulin fused to full length hemojuvelin and hemojuvelinwhich has been cleaved at a previously described proteolytic cleavagesite between aspartic acid and proline residues at amino acid 165(Niederkofler et al. J. Neurosci. 24, 808-818, 2004; Lin et al. Blood106, 2884-2889, 2005; Zhang et al. J. Biol. Chem. 280, 33885-33894,2005). A lower band at ˜40-45 kDa may represent another cleavage form.FIGS. 4B and 4C show ¹²⁵I-BMP-2 (FIG. 4B) or ¹²⁵I-BMP-4 (FIG. 4C) wasincubated overnight alone (Control) or in combination with 60 ng Hjv.Fc,in the absence (Binding) or presence of excess unlabeled BMP-2, -4, -7,or TGF-β1, followed by incubation on protein A coated plates anddetermination of bound radioactivity using a standard γ counter. Resultsare reported as the mean+/−standard deviation (n=2 to 3 in each group; *P<0.05 compared to Control: b, bar 2 P=0.0003; c, bar 2 P=0.0004; **P<0.05 compared to Binding: b, bar 3 P=0.002, bar 4 P=0.011; c, bar 3P=0.000005, bar 4 P=0.0005).

FIG. 5 shows that Hjv.Fc forms a complex with ¹²⁵I-BMP-2 in solution.the inventors incubated buffer alone (control), 60 ng Hjv.Fc or TGF-βtype I receptor ALK5.Fc with ¹²⁵I-BMP-2, with or without excessunlabeled BMP-2, in the absence or presence of the crosslinker DSS.¹²⁵I-BMP-2 bound to Hjv.Fc was precipitated with Protein A beads, andthe eluted protein complex was analyzed by nonreducing SDS-PAGE,followed by autoradiography. The band migrating at B180 kDa correspondsto the predicted size of a complex containing a dimer ofdisulfide-linked Hjv.Fc and a dimer of disulfide-linked ¹²⁵I-BMP-2.

FIGS. 6A and 6B show that hemojuvelin mediates BMP signaling via BMPtype I receptors, ALK3 and ALK6, and can be crosslinked with ALK6 at thecell surface in the presence of BMP-2. FIG. 6A shows HepG2 cells weretransfected with BRE-Luc and pRL-TK alone (bars 1, 5-7), or incombination with 40 ng/ml HJV (bars 2-4), without (bars 2, 5) or withco-transfection with 200 ng/ml cDNA encoding dominant negative BMP typeI receptor ALK3 (ALK3 DN, bars 3, 6) or ALK6 (ALK6 DN, bars 4, 7).Transfected cells were incubated in the absence (bars 1-4) or presenceof 25 ng/ml BMP-2 (bars 5-7). Cell lysates were analyzed for luciferaseactivity as in FIG. 3. Results are reported as the mean+/−standarddeviation (n=2 to 3 in each group; * P<0.05 compared to cellstransfected with Hjv alone (bar 2): bar 3 compared to 2 P=0.0000006, bar4 compared to 2 P=0.0003). FIG. 6B shows that HEK293 cells which weretransfected with cDNA encoding FLAG-tagged human hemojuvelin (FLAG-HJV)(lanes 2-3, 5-6) and/or HAtagged ALK6 (ALK6-HA) (lanes 1, 3, 4, 6).Transfected cells were incubated in the absence (lanes 1-3) or presenceof BMP-2 (lanes 4-6) followed by crosslinking with DSS. Cell lysateswere immunoprecipitated with anti-HA antibody (α-HA), andimmunoprecipitates were analyzed by Western blot with anti-FLAG antibody(α-FLAG) to demonstrate the formation of a complex between FLAG-HJV andALK6-HA in the presence of BMP-2 (lane 6). As a control to confirmprotein expression, Western blot of total cell lysates was performedwith α-FLAG and α-HA.

FIG. 7 shows that hemojuvelin mediates BMP signaling via BMPreceptor-activated Smad1. HepG2 cells were transfected with BRE-Luc andpRL-TK without (bars 1, 5-7), or in combination with, 40 ng/ml Hjv (bars2-4), in the absence (bars 1, 2, 5) or presence of 200 ng/ml cDNAencoding wild-type (WT, bars 3, 6) or dominant negative (DN) Smad1 (bars4, 7). Transfected cells were incubated in the absence (bars 1-4) orpresence of 25 ng/ml BMP-2 (bars 5-7) for 16 hours. Cell lysates wereanalyzed for luciferase activity as in FIGS. 3A-3C. Results are reportedas the mean+/−standard deviation (n=2 in each group; * P<0.05 comparedto cells transfected with Hjv alone (bar 2): bar 3 compared to bar 2P=0.002, bar 4 compared to bar 2 P=0.0024).

FIGS. 8A-8D show that hemojuvelin mutants associated withhemochromatosis have impaired BMP signaling ability. FIG. 8A shows aprotein blot of cell lysates from CHO cells transfected with cDNAencoding empty vector (‘mock’), wild-type mouse hemojuvelin (Hjv) ormutant mouse hemojuvelin G313V (G313V-Hjv) with antihemojuvelin antibody(α-HJV). Blots were stripped and reprobed with anti-β-actin antibody(α-β-actin) as a loading control. FIGS. 8B-8D show cells transfectedwith BRE-Luc, pRL-TK in the presence of increasing amounts of Hjv orG313V-Hjv. HepG2 (FIG. 8B), or Hep3B cells (FIG. 8C, 8D) weretransfected with BRE-Luc, pRL-TK and increasing amounts of Hjv orG313V-Hjv (b, 0.04-400 ng ml-1) or, alternatively, cDNA encodingFlag-tagged wild-type human hemojuvelin (Flag-HJV) or Flag-tagged mutanthuman hemojuvelin G99V (Flag-G99V-HJV) (c, 2-200 ng ml-1; d, 20-800 ngml-1). Cell lysates were analyzed for luciferase activity as in FIG. 1(FIGS. 8B, 8C) or by protein blot with α-HJV (FIG. 8D). Blots werestripped and reprobed with α-β-actin as a loading control. (b,c) Resultsare expressed as mean±s.d. n=2 in each group. * P<0.05 (Flag-HJV versuscontrol in FIG. 8C). ** P<0.05 (G313V-Hjv versus Hjv in b, andFlag-G99V-HJV versus Flag-HJV in c). Exact P-values are shown abovepoints in FIG. 8C. In FIG. 8B, P-values are 0.0016, 0.0039, 0.058 and0.0008 for open circles 4-7, respectively.

FIG. 9 shows that Hfe2^(−/−) livers show decreased basal BMP signalingcompared with wild-type livers. Liver lysates from wild-type (+/+) orHfe2^(−/−) mice (−/−) were analyzed by protein blot with antibody tophosphorylated Smad1/5/8. Blots were stripped and reprobed with antibodyto Smad1 and antibody to β-actin as loading controls. Chemiluminescencewas quantified using IPLab Spectrum software to calculate the ratio(mean±s.d.) of phosphorylated Smad1/5/8 (p-Smad) relative to total Smad1(left) and relative to β-actin (right). n=3 in each group; * P<0.05 forlivers from Hfe2^(−/−) mice compared with wild-type mice.

FIGS. 10A-10D show that hemojuvelin positively regulates hepcidin mRNAexpression. FIGS. 10A and 10B show Hep3B cells which were transfectedwith an empty vector (control) or increasing amounts of cDNA encodingFlag-HJV (FIG. 10A) or 40 ng ml⁻¹ Flag-HJV or Flag-G99V-HJV (FIG. 10B).Total RNA was isolated and real-time quantification of hepcidin mRNAtranscripts was performed using a two-step RT-PCR. Quantitativereal-time PCR for β-actin was performed in parallel as an internalcontrol. Samples were analyzed in triplicate and are reported as theratio of mean values for hepcidin to ββ-actin. FIGS. 10C and 10D show afirefly luciferase reporter driven by 2.7 kb of the proximal hepcidinpromoter which was cotransfected into Hep3B cells with pRL-TK to controlfor transfection efficiency, either alone or with increasingconcentrations of Flag-HJV or Flag-G99V-HJV (2-20 ng ml⁻¹; FIG. 10C) oralternatively Hjv or G313V-Hjv (2-200 ng ml⁻¹; d). Relative luciferaseactivity was calculated as in FIGS. 2A and 2B. Results are reported asmean±s.d. n=3 in each group. * P<0.05 (Flag-HJV versus control in a-cand Hjv versus control in FIG. 10D). ** P<0.05 (Flag-G99V-HJV versusFlag-HJV or G313V-Hjv versus Hjv in FIG. 10B-10D). Exact P-values areshown above points and bars. In FIG. 10D, P=0.004 and 0.05 for circles 3and 4, respectively.

FIGS. 11A-11D show that BMP-2 positively regulates hepcidin mRNAexpression. FIGS. 11A-11C show HepG2 cells (11A, 11C) or Hep3B cells(11B) were incubated in the absence or presence of 1 mg ml⁻¹ noggin for48 h, 50 ng ml⁻¹ BMP-2 for 16 h (FIG. 11A, 11B) or 50 ng ml⁻¹ BMP-2 for0-16 h (FIG. 11C). Quantitative real-time PCR for hepcidin and β-actinwere performed as described in FIG. 5. FIG. 11D shows cells which weretransfected with the hepcidin promoter luciferase construct and pRL-TKwere incubated in the absence or presence of increasing concentrationsof BMP-2 (6-150 ng ml⁻¹) for 16 h. Relative luciferase activity wascalculated as in FIG. 1. Results are reported as mean±s.d. n=2 to 4 ineach group. * P<0.05 compared with control.

FIG. 12 shows that the proximal hepcidin promoter is conserved amongmammals and contains putative BMP-responsive elements. Genome sequenceswere retrieved from the UCSC Genome Bioinformatics Group website (worldwide web site: “genome-dot-ucsc-dot-edu”) following a BLAT Search oneach of the genome assemblies using human hepcidin cDNA (GenBankaccession number NM_(—)021175) as the query. Shown is the alignedsequence of the proximal hepcidin promoter in human (SEQ ID NO: 51),chimp (SEQ ID NO: 52), dog (SEQ ID NO: 53), rat (SEQ ID NO: 54), andmouse (SEQ ID NO: 55). Putative common mediator Smad4 binding elements(Shi & Massague, Cell 113, 685-700, 2003; Korchynskyi & ten Dijke. J.Biol. Chem. 277, 4883-4891, 2002; Dennler et al. EMBO J. 17, 3091-3100,1998) are shown in black. Putative BMP receptor-activated Smad bindingelements (Korchynskyi & ten Dijke, J. Biol. Chem. 277, 4883-4891, 2002;Henningfeld et al. J. Biol. Chem. 275, 21827-21835, 2000; Ishida et al.J. Biol. Chem. 275, 6075-6079, 2000) are shown in gray. Putative TATAbox, transcription initiation start site (+1) and translation initiationcodon (Courselaud et al. J. Biol. Chem. 277, 41163-41170, 2002) areindicated in bold.

FIG. 13 shows that BMP-2 regulation of hepcidin expression is notaffected by cycloheximide. HepG2 cells were incubated without (Control)or with 10 μg/ml cycloheximide for 30 minutes followed by incubationwithout or with 50 ng/ml BMP-2 for 6 hours as indicated. Quantitativereal-time PCR for hepcidin and β-actin were performed as described inFIGS. 10A-10D. Results are reported as the mean+/−standard deviation(n=2 in each group).

FIGS. 14A-14D show that hepcidin induction by BMP-2 is enhanced byhemojuvelin and blunted in Hfe2^(−/−) hepatocytes. FIGS. 14A-14C showHep3B cells which were transfected with the hepcidin promoter luciferaseconstruct and pRL-TK were incubated either (i) alone, or (ii) in thepresence of 30 ng ml⁻¹ BMP-2 alone (as shown by a “+”), or (iii) in thepresence of 30 ng ml⁻¹ BMP-2 after cotransfection with increasingconcentrations (i.e. 2 or 20 or 200 ng/ml) of cDNA encoding Flag-HJV,Flag-G99V-HJV, Hjv or G313V-Hjv as indicated. Relative luciferaseactivity was determined as in FIGS. 2A and 2B. Values are mean±s.d.n=2-4 in each group. * P<0.05 for Flag-HJV versus control in a-c; **P<0.05 for Flag-G99V-HJV versus Flag-HJV in FIGS. 14B and G313V-Hjvversus Hjv in 14C. In FIG. 14A, bar 4 P=0.0008, bar 5 P=0.0001; FIG.14B, square 3 P=0.0004, square 4 P=0.00006; circle 3 P=0.003, circle 4P=0.0004; FIG. 14C, square 4 P=0.007, circle 4 P=0.007. FIG. 14D showsprimary hepatocytes isolated from Hfe2^(+/+) or Hfe2^(−/−) mice whichwere incubated in the absence (control) or presence of 10 ng ml⁻¹ BMP-2for 12 h, followed by RNA blot analysis for hepcidin mRNA. Expressionwas quantified using a phosphorimager and normalized to β-actin as aloading control. Ratios of hepcidin to β-actin mRNA are shown as amultiple of values for control hepatocytes. Values are mean±s.d. n=3 ineach group. * P<0.05 for BMP-2-stimulated hepatocytes versus control; **P<0.05 for Hfe2^(−/−) versus Hfe2^(+/+). For Hfe2^(+/+), P=0.001compared with control, and for Hfe2^(−/−), P=0.003 compared with controland P=0.01 compared with Hfe2^(+/+).

FIGS. 15A and 15B show induction of hepcidin expression by TGF-β/BMPsuperfamily ligands. FIG. 15A shows Hep3B cells which were transfectedwith a hepcidin promoter firefly luciferase reporter and a controlRenilla luciferase vector (pRL-TK). Transfected cells were incubatedeither alone (Control) or with 50 ng/ml BMP or GDF ligands, 5 ng/mlTGF-β ligands, or 30 ng/ml Activin A as indicated. Cell lysates wereanalyzed for luciferase activity. Relative luciferase activity wascalculated as the ratio of firefly to Renilla luciferase values tocontrol for transfection efficiency, and is expressed as the foldincrease compared with Control. Results are reported as themean+/−standard deviation (n=2 to 3 in each group). FIG. 15B shows Hep3Bcells which were treated with BMP, GDF, TGF-β, or Activin A ligands asin A. Total RNA was analyzed by quantitative real-time RT-PCR forhepcidin mRNA expression and β-actin mRNA expression. Samples wereanalyzed in triplicate, and are reported as the ratio of mean values forhepcidin to β-actin.

FIGS. 16A and 16B show that BMP-2 administration in mice increaseshepcidin mRNA expression and decreases serum iron. 12956/SvEvTac micewere injected retro-orbitally with 1 mg/kg BMP-2 (n=8) or an equalvolume of vehicle alone (n=7). Four hours after injection, blood andlivers were harvested. FIG. 16A shows total mRNA which was isolated fromlivers and analyzed by quantitative real-time RTPCR for hepcidin mRNAexpression relative to GAPDH mRNA expression as an internal control.FIG. 16B shows serum iron which was measured by colorimetric assay.FIGS. 16A and 16B show the results reported as the mean+/−standarddeviation, * P<0.05 for BMP-2 treated mice compared with Control.

FIGS. 17A-17D show that soluble HJV.Fc inhibits basal hepcidinexpression and selectively inhibits BMP induction of hepcidinexpression. FIG. 17A shows a western blot of purified soluble HJV.Fcfusion protein with anti-hemojuvelin antibody (α-HJV) and anti-Fcantibody (α-Fc). FIGS. 17B and 17C show HepG2 cells which were incubatedalone (Control) or with 25 μg/ml HJV.Fc alone, 25 ng/ml BMP-2 alone, ora combination of HJV.Fc and BMP-2 as indicated. Total RNA was isolatedand quantitative real-time PCR (RT-PCR) for hepcidin mRNA relative toβ-actin mRNA was performed as in FIG. 15. Results are reported as themean+/−standard deviation (n=3 in each group, * P<0 05 for HJV.Fccompared with Control in FIG. 17B, or for HJV.Fc plus BMP-2 comparedwith BMP-2 alone in FIG. 17C). FIG. 17D shows Hep3B cells which weretransfected with the hepcidin promoter luciferase construct and pRL-TK.Transfected cells were incubated alone or with 5 ng/ml BMP-9, 50 ng/mlBMP-5, or 25 ng/ml BMP-2, -4, -6, or -7 ligands, either alone or incombination with 0.2 to 25 μg/ml HJV.Fc as indicated followed bymeasurement of relative luciferase activity as in FIG. 15. Results arereported as the mean+/−standard deviation of the percent decrease inrelative luciferase activity for cells treated with BMP ligands incombination with HJV.Fc compared with cells treated with the respectiveBMP ligands alone (n=2 in each group).

FIGS. 18A-18C show siRNA inhibition of endogenous BMP ligands decreasesbasal hepcidin expression. FIG. 18A show the expression of endogenousBMP ligands in HepG2 cells as measured by RT-PCR. PCR of purifiedplasmid cDNAs expressing BMP ligands were used as positive controls(Control). FIGS. 18B and 18C show HepG2 cells which were transfectedwith BMP ligand siRNA's or a Control scrambled siRNA as indicated. TotalRNA was analyzed for BMP ligand expression (FIG. 18B) or hepcidinexpression (FIG. 18C) relative to β-actin expression by real-timequantitative RT-PCR. Results are reported as the mean+/−standarddeviation of the percent decrease in the ratio of hepcidin or BMP ligandto β-actin 35 for cells treated with various BMP siRNAs compared withcells treated with Control siRNA; n=3 to 6 per group; * P<0.05.

FIGS. 19A-19G show soluble HJV.Fc administration in mice decreaseshepatic phosphorylated Smad1/5/8 expression, decreases hepcidinexpression, increases serum iron, increases liver iron content, anddecreases spleen iron content. 129S6/SvEvTac mice received anintraperitoneal injection of 25 mg/kg HJV.Fc or normal saline (Control)three times weekly for three weeks. FIG. 19A shows liver lysates whichwere analyzed for phosphorylated Smad1/5/8 expression by Western blot.Blots were stripped and re-probed for total Smad1 expression and β-actinexpression as loading controls. Chemiluminescence was quantitated by IPLab Spectrum software for phosphorylated Smad1/5/8 relative to totalSmad1 expression. FIG. 19B shows total mRNA which was isolated fromlivers and analyzed by quantitative real-time PCR for hepcidin mRNAexpression relative to GAPDH mRNA expression as an internal control.FIG. 19C shows spleen membrane preparations which were analyzed forferroportin expression by Western blot. Blots were stripped andre-probed for β-actin expression as a loading control. FIGS. 19D and 19Eshow the measurement and levels of serum iron and transferrinsaturation. FIGS. 19F and 19G shows the quantitation of liver (FIG. 19F)and spleen (FIG. 19G) tissue iron content. Results are expressed asmean+/−standard deviation, n=3 mice per group, * P<0.05 for HJV.Fctreated mice compared with Control mice.

FIG. 20 shows that soluble HJV.Fc inhibits IL-6 induction of hepcidinexpression. HepG2 cells were incubated for 16 hours under controlconditions, with 100 ng/ml IL-6, or with 100 ng/ml IL-6 in combinationwith HJV.Fc after pre-incubation with HJV.Fc for 1 hour as indicated.Total RNA was analyzed for hepcidin expression relative to β-actinexpression by quantitative real-time RT-PCR. Results are expressed asmean+/−standard deviation, n=3 per group, * P=0.003 for IL-6 treatedcells compared with Control cells, ** P=0.0006 for cells treated withHJV.Fc in combination with IL-6 compared with cells treated with IL-6alone.

FIG. 21 shows the sequences of an exemplary HJV.Fc fusion protein. FIG.21A shows Human HJV.Fc fusion (HJV 33-399) with extracellular signalsequence and FLAG tag in place of N-terminal sequence and GPI anchoringdomain removed (SEQ ID NO:1). FIGS. 21B-21D shows three human HJVisoforms (SEQ ID NOS:2-4), with FIG. 21B showing Human HJV isoform A(SEQ ID NO:2), FIG. 21C showing Human HJV isoform B (SEQ ID NO:3); FIG.21D showing Human HJV isoform C (SEQ ID NO:4). FIG. 21E shows mouse HJV(SEQ ID NO:5). FIG. 21F shows the human Fc sequence (SEQ ID NO:6), andFIG. 21G shows an exemplary HJV.Fc fusion protein with enhancedproteolytic stability (HJV-D172A.Fc) which is a non-cleavable form ofthe HJV.Fc protein (SEQ ID NO:7). FIGS. 21H and 21I shows nucleic acidsequences corresponding to the HJV.Fc (SEQ ID NO:8) and HJV-D172A.Fcfusion proteins (SEQ ID NO:9), with FIG. 21H showing the DNA sequenceencoding human HJV.Fc fusion protein (SEQ ID NO:8) and FIG. 21I showingDNA sequence encoding human HJV-D172A.Fc fusion protein (SEQ ID NO:9).FIG. 21J shows the amino acid sequence of codon optimized human HJV-Fcfusion, with extracellular signal sequence and the GPI anchoring domainremoved (SEQ ID NO:10), and FIG. 21K shows codon-optimized DNA sequenceencoding human HJV.Fc fusion protein (SEQ ID NO:11). In FIG. 21K, theexemplary DNA linkers are shown, a -BamHI/HindIII-linker site at the 5′end and a -EcoRI/NotI-linker site at the 3′ (shown sites areunderlined); with the Kozak sequence in lower case, the start ATG codonin bold; and the TGA Stop Codon in bold.

FIGS. 22A-22B shows that a lower dose of soluble human HJV.Fcadministration increases serum iron. 12956/SvEvTac mice received anintraperitoneal injection of 5 mg/kg HJV.Fc or normal saline (Control)three times weekly for three weeks. FIG. 22A shows serum iron and FIG.22B shows transferrin saturation. Results are expressed asmean+/−standard deviation, n=3 mice per group, * P<0.05 for HJV.Fctreated mice compared with Control mice.

FIG. 23 shows the amino acid sequence alignment and comparison of mouseHJV (DL-2) with other mouse homologue members of the RGM family. Aminoacid sequence alignment of mouse HJV (mDL-2) (SEQ ID NO: 56), and mouseDRAGON (mRGMb) (SEQ ID NO: 57) and mouse DL-1 (mDL-1, mRGMa) (SEQ ID NO:58) are shown, with the conserved amino acids residues shown in blackboxes.

FIG. 24 shows the amino acid sequence alignment and comparison of partof the amino acid sequence of human HJV (SEQ ID NO: 59) and mouse RGMc(SEQ ID NO: 60). Human HJV is 88% identical and 92% similar to mouseRGMc, with conserved amino acids shown in black boxes. Both have apredicted signal peptide cleavage site (gray arrow), three consensussequences for N-linked glycosylation (solid line), and twelve cysresidues conserved in HJV and all of the mouse RGM family of proteins(asterisk). Both HJV and RGMc have one predicted acid sensitiveautocatalytic cleavage site (black arrow) and a predicted GPI-linkedsite (white arrow). An anti-peptide antibody can be generated to thesequence denoted by a dashed line (FIG. 24 is reproduced from Zhang etal, 2005; JBC).

FIG. 25 shows a prediction of residue conservation and location based onConSeq. Sequence shown in human HJV (which is based on GenBank AccessionNo Q6ZVN8 (SEQ ID NO:61) with the signal and propeptides removed.Protein regions, as defined in the text, are shown above the sequence.Residues that are more conserved are shown in increasingly darkerbackground with white text; more variable sequences are shown in blacktext. Below the sequence, “e” indicates a residue predicted to beexposed (surface) and “b” indicates a buried residue. “s” and “f”represent ConSeq's prediction of residues of “structural” or“functional” importance. (FIG. 25 is reproduced from Camus et al, J MolEvol, 2007; 65:68-81).

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The inventors have identified a novel therapeutic, HJV.Fc, useful in thetreatment of conditions involving hepcidin regulation (e.g.,iron-related disorders such as those described herein). Accordingly thepresent invention provides HJV fusion proteins (e.g., HJV.Fc),pharmaceutical compositions containing such proteins, polynucleotidesencoding such proteins, and methods for treating HJV-related disorderssuch as iron-related disorders (e.g., those described herein).

One aspect of the present invention relates to a soluble form of HJV. Insome embodiments, such a soluble form of HJV is where polypeptides offull length HJV, or a fragment of HJV are fused to a second peptide, forexample a IgG1 Fc or fragment thereof, and is referred to as “HJV.Fc”herein. In some embodiments, the HJV which is fused to a secondpolypeptide (i.e. the first fusion partner) can be a fragment of HJV,such as HJV lacking the C-terminal GPI domain and/or the N-terminalsignal sequence or alternatively, the HJV can be a functional derivativeof HJV or a functional variant of HJV, as these terms are definedherein. In some embodiments, the HJV proteins useful for fusion to afirst fusion partner can be any isoform of HJV, for example HJV proteinscorresponding to SEQ ID NOS: 2, 3, 4 or 5, respectively, or functionalfragments or functional derivatives or a functional variants of HJVpolypeptides corresponding to SEQ ID NOs: 2 to 5.

Additionally, a fusion partner bound to HJV, or functional fragments,derivatives or variants thereof can be an IgG1 Fc fragment, such as theFc fragment corresponding to SEQ ID NO: 6 or functional fragments orderivatives or variants thereof. In alternative embodiments, the firstfusion partner can be any polypeptide sequence that increases thestability of the HJV polypeptide or functional derivative, functionalfragment or functional variant thereof. For example, fusion of HJVpolypeptides to a serum protein, e.g., serum albumin, can increase thecirculating half-life of a HJV polypeptide.

In some embodiments, an example of a HJV.Fc as disclosed hereincorresponds to SEQ ID NO:7 or a functional variant or functionalderivative thereof, where SEQ ID NO:7 is the amino acid sequence forhuman HJV.Fc with a non-cleavable variant of HJV without the GPIanchoring domain fused to a Fc fragment.

In another embodiment, a HJV.Fc as disclosed herein corresponds to SEQID NO:10 or a functional variant or functional derivative thereof, whereSEQ ID NO:10 is the amino acid sequence for human HJV.Fc where HJVwithout the GPI anchoring domain, has been codon-optimized for optimalexpression in mammalian cells is fused to a Fc fragment.

In another embodiment, a HJV.Fc as disclosed herein corresponds to SEQID NO:1 or a functional variant or functional derivative thereof, whereSEQ ID NO:1 is the amino acid sequence for human HJV.Fc with HJVcomprising an extracellular signal sequence and FLAG tag, but with theGPI anchoring domain removed.

In one embodiment, the HJV fusion polypeptide comprises a human HJVpolypeptide and a first fusion partner. In one embodiment, the HJVfusion polypeptide consists essentially of a human HJV polypeptide and afirst fusion partner. In one embodiment, the HJV fusion polypeptideconsists of a human HJV polypeptide and a first fusion partner.

In another embodiment, the HJV fusion polypeptide comprises human HJVpolypeptide which comprises, or alternatively, consists of a polypeptidehaving the sequence of SEQ ID NO: 2 or 3, or 4, or a functional fragmentthereof, or a HJV functional fragment of SEQ ID NO: 7 or 10. In anotherembodiment, the nucleic acid construct comprises a polypeptide encodedby the sequence corresponding to SEQ ID NO: 8, 9 or 11.

Definitions

For convenience, certain terms employed in the entire application(including the specification, examples, and appended claims) arecollected here. Unless defined otherwise, all technical and scientificterms used herein have the same meaning as commonly understood by one ofordinary skill in the art to which this invention belongs.

By “human Fc” is meant a polypeptide with an amino acid sequence atleast about 50%, or at least about 60%, or at least about 70%, or atleast about 80%, or at least about 90%, or at least about 95%, or atleast about 96%, or at least about 97%, or at least about 98%, or atleast about 99% identical to the sequence of SEQ ID NO:6 (FIG. 21).

By a “polynucleotide encoding human Fc” is meant a polynucleotide thatencodes a polypeptide sequence having at least about 50%, or at leastabout 60%, or at least about 70%, or at least about 80%, or at leastabout 90%, or at least about 95%, or at least about 96%, or at leastabout 97%, or at least about 98%, or at least about 99% identity to thesequence of SEQ ID NO:6 (FIG. 21).

By “hemojuvelin” or “HJV” is meant a polypeptide having an amino acidsequence at least about 60%, or at least about 70%, or at least about80%, or at least about 90%, or at least about 95%, or at least about96%, or at least about 97%, or at least about 98%, or at least about 99%identical to any of SEQ ID NOs: 2 to 5 (FIG. 21).

By a “polynucleotide encoding hemojuvelin” is meant a polynucleotideencoding a polypeptide having at least about 60%, or at least about 70%,or at least about 80%, or at least about 90%, or at least about 95%, orat least about 96%, or at least about 97%, or at least about 98%, or atleast about 99% sequence identity to any of the amino acid sequencescorresponding to SEQ ID NOs: 2 to 5 (FIG. 21).

The term “wild type” refers to the naturally-occurring polynucleotidesequence encoding a protein, or a portion thereof, or protein sequence,or portion thereof, respectively, as it normally exists in vivo.Accordingly, as disclosed herein, the wild type amino acid sequence forthe human HJV protein corresponds to SEQ ID NOs: 2, 3 and 4, which referto human HJV isoforms A, B and C respectively.

The term “soluble HJV polypeptide” as used herein refers to a HJVpolypeptide that does not comprise at least part of, or all of, theamino acids which allow it to functionally bind to the membrane. Anexample of a soluble HJV polypeptide is a HJV with the removal of theGPI anchor.

The term “mutant” refers to any change in the genetic material of anorganism, in particular a change (i.e., deletion, substitution,addition, or alteration) in a wild-type polynucleotide sequence or anychange in a wild-type protein sequence. The term “variant” is usedinterchangeably with “mutant”. Although it is often assumed that achange in the genetic material results in a change of the function ofthe protein, the terms “mutant” and “variant” refer to a change in thesequence of a wild-type protein regardless of whether that change altersthe function of the protein (e.g., increases, decreases, imparts a newfunction), or whether that change has no effect on the function of theprotein (e.g., the mutation or variation is silent). The term mutationis used interchangeably herein with polymorphism in this application.

The terms “polypeptide” and “protein” are used interchangeably to referto a polymer of amino acid residues, and are not limited to a minimumlength. Peptides, oligopeptides, dimers, multimers, and the like, arealso composed of linearly arranged amino acids linked by peptide bonds,and whether produced biologically, recombinantly, or synthetically andwhether composed of naturally occurring or non-naturally occurring aminoacids, are included within this definition. Both full-length proteinsand fragments thereof are encompassed by the definition. The terms alsoinclude co-translational (e.g., signal peptide cleavage) andpost-translational modifications of the polypeptide, such as, forexample, disulfide-bond formation, glycosylation, acetylation,phosphorylation, proteolytic cleavage (e.g., cleavage by furins ormetalloproteases), and the like. Furthermore, for purposes of thepresent invention, a “polypeptide” refers to a protein that includesmodifications, such as deletions, additions, and substitutions(generally conservative in nature as would be known to a person in theart), to the native sequence, as long as the protein maintains thedesired activity. These modifications can be deliberate, as throughsite-directed mutagenesis, or can be accidental, such as throughmutations of hosts that produce the proteins, or errors due to PCRamplification or other recombinant DNA methods. Polypeptides or proteinsare composed of linearly arranged amino acids linked by peptide bonds,but in contrast to peptides, has a well-defined conformation. Proteins,as opposed to peptides, generally consist of chains of 50 or more aminoacids. For the purposes of the present invention, the term “peptide” asused herein typically refers to a sequence of amino acids of made up ofa single chain of D- or L-amino acids or a mixture of D- and L-aminoacids joined by peptide bonds. Generally, peptides contain at least twoamino acid residues and are less than about 50 amino acids in length.

The incorporation of non-natural amino acids, including syntheticnon-native amino acids, substituted amino acids, or one or more D-aminoacids into the peptides (or other components of the composition, withexception for protease recognition sequences) is desirable in certainsituations. D-amino acid-containing peptides exhibit increased stabilityin vitro or in vivo compared to L-amino acid-containing forms. Thus, theconstruction of peptides incorporating D-amino acids can be particularlyuseful when greater in vivo or intracellular stability is desired orrequired. More specifically, D-peptides are resistant to endogenouspeptidases and proteases, thereby providing better oral trans-epithelialand transdermal delivery of linked drugs and conjugates, improvedbioavailability of membrane-permanent complexes (see below for furtherdiscussion), and prolonged intravascular and interstitial lifetimes whensuch properties are desirable. The use of D-isomer peptides can alsoenhance transdermal and oral trans-epithelial delivery of linked drugsand other cargo molecules. Additionally, D-peptides cannot be processedefficiently for major histocompatibility complex class II-restrictedpresentation to T helper cells, and are therefore less likely to inducehumoral immune responses in the whole organism. Peptide conjugates cantherefore be constructed using, for example, D-isomer forms of cellpenetrating peptide sequences, L-isomer forms of cleavage sites, andD-isomer forms of therapeutic peptides. In some embodiments, the HJV.Fcare comprised of D- or L-amino acid residues, as use of naturallyoccurring L-amino acid residues has the advantage that any break-downproducts should be relatively non-toxic to the cell or organism.

In yet a further embodiment, the HJV proteins or fragments orderivatives thereof can be a retro-inverso peptides. A “retro-inversopeptide” refers to a peptide with a reversal of the direction of thepeptide bond on at least one position, i.e., a reversal of the amino-and carboxy-termini with respect to the side chain of the amino acid.Thus, a retro-inverso analogue has reversed termini and reverseddirection of peptide bonds while approximately maintaining the topologyof the side chains as in the native peptide sequence. The retro-inversopeptide can contain L-amino acids or D-amino acids, or a mixture ofL-amino acids and D-amino acids, up to all of the amino acids being theD-isomer. Partial retro-inverso peptide analogues are polypeptides inwhich only part of the sequence is reversed and replaced withenantiomeric amino acid residues. Since the retro-inverted portion ofsuch an analogue has reversed amino and carboxyl termini, the amino acidresidues flanking the retro-inverted portion are replaced byside-chain-analogous α-substituted geminal-diaminomethanes andmalonates, respectively. Retro-inverso forms of cell penetratingpeptides have been found to work as efficiently in translocating acrossa membrane as the natural forms. Synthesis of retro-inverso peptideanalogues are described in Bonelli, F. et al., Int J Pept Protein Res.24(6):553-6 (1984); Verdini, A. and Viscomi, G. C., J. Chem. Soc. PerkinTrans. 1:697-701 (1985); and U.S. Pat. No. 6,261,569, which areincorporated herein in their entirety by reference. Processes for thesolid-phase synthesis of partial retro-inverso peptide analogues havebeen described (EP 97994-B) which is also incorporated herein in itsentirety by reference.

The terms “homology”, “identity” and “similarity” refer to the degree ofsequence similarity between two peptides or between two optimallyaligned nucleic acid molecules. Homology and identity can each bedetermined by comparing a position in each sequence which can be alignedfor purposes of comparison. For example, it is based upon using astandard homology software in the default position, such as BLAST,version 2.2.14. When an equivalent position in the compared sequences isoccupied by the same base or amino acid, then the molecules areidentical at that position; when the equivalent site occupied by similaramino acid residues (e.g., similar in steric and/or electronic naturesuch as, for example conservative amino acid substitutions), then themolecules can be referred to as homologous (similar) at that position.Expression as a percentage of homology/similarity or identity refers toa function of the number of similar or identical amino acids atpositions shared by the compared sequences, respectfully. A sequencewhich is “unrelated” or “non-homologous” shares less than 40% identity,though preferably less than 25% identity with the sequences as disclosedherein.

As used herein, the term “sequence identity” means that twopolynucleotide or amino acid sequences are identical (i.e., on anucleotide-by-nucleotide or residue-by-residue basis) over thecomparison window. The term “percentage of sequence identity” iscalculated by comparing two optimally aligned sequences over the windowof comparison, determining the number of positions at which theidentical nucleic acid base (e.g., A, T. C, G. U. or I) or residueoccurs in both sequences to yield the number of matched positions,dividing the number of matched positions by the total number ofpositions in the comparison window (i.e., the window size), andmultiplying the result by 100 to yield the percentage of sequenceidentity.

The terms “substantial identity” as used herein denotes a characteristicof a polynucleotide or amino acid sequence, wherein the polynucleotideor amino acid comprises a sequence that has at least 85% sequenceidentity, preferably at least 90% to 95% sequence identity, more usuallyat least 99% sequence identity as compared to a reference sequence overa comparison window of at least 18 nucleotide (6 amino acid) positions,frequently over a window of at least 24-48 nucleotide (8-16 amino acid)positions, wherein the percentage of sequence identity is calculated bycomparing the reference sequence to the sequence which can includedeletions or additions which total 20 percent or less of the referencesequence over the comparison window. The reference sequence can be asubset of a larger sequence. The term “similarity”, when used todescribe a polypeptide, is determined by comparing the amino acidsequence and the conserved amino acid substitutes of one polypeptide tothe sequence of a second polypeptide.

As used herein, the terms “homologous” or “homologues” are usedinterchangeably, and when used to describe a polynucleotide orpolypeptide, indicates that two polynucleotides or polypeptides, ordesignated sequences thereof, when optimally aligned and compared, forexample using BLAST, version 2.2.14 with default parameters for analignment (see herein) are identical, with appropriate nucleotideinsertions or deletions or amino-acid insertions or deletions, in atleast 70% of the nucleotides, usually from about 75% to 99%, and morepreferably at least about 98 to 99% of the nucleotides. The term“homolog” or “homologous” as used herein also refers to homology withrespect to structure and/or function. With respect to sequence homology,sequences are homologs if they are at least 50%, at least 60 at least70%, at least 80%, at least 90%, at least 95% identical, at least 97%identical, or at least 99% identical. Determination of homologs of thegenes or peptides of the present invention can be easily ascertained bythe skilled artisan.

The term “substantially homologous” refers to sequences that are atleast 90%, at least 95% identical, at least 96%, identical at least 97%identical, at least 98% identical or at least 99% identical. Homologoussequences can be the same functional gene in different species.Determination of homologs of the genes or peptides of the presentinvention can be easily ascertained by the skilled artisan.

For sequence comparison, typically one sequence acts as a referencesequence, to which test sequences are compared. When using a sequencecomparison algorithm, test and reference sequences are input into acomputer, subsequence coordinates are designated, if necessary, andsequence algorithm program parameters are designated. The sequencecomparison algorithm then calculates the percent sequence identity forthe test sequence(s) relative to the reference sequence, based on thedesignated program parameters.

Optimal alignment of sequences for comparison can be conducted, forexample, by the local homology algorithm of Smith and Waterman (Adv.Appl. Math. 2:482 (1981), which is incorporated by reference herein), bythe homology alignment algorithm of Needleman and Wunsch (J. Mol. Biol.48:443-53 (1970), which is incorporated by reference herein), by thesearch for similarity method of Pearson and Lipman (Proc. Natl. Acad.Sci. USA 85:2444-48 (1988), which is incorporated by reference herein),by computerized implementations of these algorithms (e.g., GAP, BESTFIT,FASTA, and TFASTA in the Wisconsin Genetics Software Package, GeneticsComputer Group, 575 Science Dr., Madison, Wis.), or by visualinspection. (See generally Ausubel et al. (eds.), Current Protocols inMolecular Biology, 4th ed., John Wiley and Sons, New York (1999)).

One example of a useful algorithm is PILEUP. PILEUP creates a multiplesequence alignment from a group of related sequences using progressive,pairwise alignments to show the percent sequence identity. It also plotsa tree or dendogram showing the clustering relationships used to createthe alignment. PILEUP uses a simplification of the progressive alignmentmethod of Feng and Doolittle (J. Mol. Evol. 25:351-60 (1987), which isincorporated by reference herein). The method used is similar to themethod described by Higgins and Sharp (Comput. Appl. Biosci. 5:151-53(1989), which is incorporated by reference herein). The program canalign up to 300 sequences, each of a maximum length of 5,000 nucleotidesor amino acids. The multiple alignment procedure begins with thepairwise alignment of the two most similar sequences, producing acluster of two aligned sequences. This cluster is then aligned to thenext most related sequence or cluster of aligned sequences. Two clustersof sequences are aligned by a simple extension of the pairwise alignmentof two individual sequences. The final alignment is achieved by a seriesof progressive, pairwise alignments. The program is run by designatingspecific sequences and their amino acid or nucleotide coordinates forregions of sequence comparison and by designating the programparameters. For example, a reference sequence can be compared to othertest sequences to determine the percent sequence identity relationshipusing the following parameters: default gap weight (3.00), default gaplength weight (0.10), and weighted end gaps.

Another example of an algorithm that is suitable for determining percentsequence identity and sequence similarity is the BLAST algorithm, whichis described by Altschul et al. (J. Mol. Biol. 215:403-410 (1990), whichis incorporated by reference herein). (See also Zhang et al., NucleicAcid Res. 26:3986-90 (1998); Altschul et al., Nucleic Acid Res.25:3389-402 (1997), which are incorporated by reference herein).Software for performing BLAST analyses is publicly available through theNational Center for Biotechnology Information internet web site. Thisalgorithm involves first identifying high scoring sequence pairs (HSPs)by identifying short words of length W in the query sequence, whicheither match or satisfy some positive-valued threshold score T whenaligned with a word of the same length in a database sequence. T isreferred to as the neighborhood word score threshold (Altschul et al.(1990), supra). These initial neighborhood word hits act as seeds forinitiating searches to find longer HSPs containing them. The word hitsare then extended in both directions along each sequence for as far asthe cumulative alignment score can be increased. Extension of the wordhits in each direction is halted when: the cumulative alignment scorefalls off by the quantity X from its maximum achieved value; thecumulative score goes to zero or below, due to the accumulation of oneor more negative-scoring residue alignments; or the end of eithersequence is reached. The BLAST algorithm parameters W, T, and Xdetermine the sensitivity and speed of the alignment. The BLAST programuses as defaults a word length (W) of 11, the BLOSUM62 scoring matrix(see Henikoff and Henikoff, Proc. Natl. Acad. Sci. USA 89:10915-9(1992), which is incorporated by reference herein) alignments (B) of 50,expectation (E) of 10, M=5, N=−4, and a comparison of both strands.

In addition to calculating percent sequence identity, the BLASTalgorithm also performs a statistical analysis of the similarity betweentwo sequences (see, e.g., Karlin and Altschul, Proc. Natl. Acad. Sci.USA 90:5873-77 (1993), which is incorporated by reference herein). Onemeasure of similarity provided by the BLAST algorithm is the smallestsum probability (P(N)), which provides an indication of the probabilityby which a match between two nucleotide or amino acid sequences wouldoccur by chance. For example, an amino acid sequence is consideredsimilar to a reference amino acid sequence if the smallest sumprobability in a comparison of the test amino acid to the referenceamino acid is less than about 0.1, more typically less than about 0.01,and most typically less than about 0.001.

The term “variant” as used herein refers to a peptide or nucleic acidthat differs from the naturally occurring polypeptide or nucleic acid byone or more amino acid or nucleic acid deletions, additions,substitutions or side-chain modifications, yet retains one or morespecific functions or biological activities of the naturally occurringmolecule. Amino acid substitutions include alterations in which an aminoacid is replaced with a different naturally-occurring or anon-conventional amino acid residue. Such substitutions may beclassified as “conservative”, in which case an amino acid residuecontained in a polypeptide is replaced with another naturally occurringamino acid of similar character either in relation to polarity, sidechain functionality or size. Substitutions encompassed by the presentinvention may also be “non conservative”, in which an amino acid residuewhich is present in a peptide is substituted with an amino acid havingdifferent properties, such as naturally-occurring amino acid from adifferent group (e.g., substituting a charged or hydrophobic amino; acidwith alanine), or alternatively, in which a naturally-occurring aminoacid is substituted with a non-conventional amino acid. In someembodiments amino acid substitutions are conservative. Also encompassedwithin the term variant when used with reference to a polynucleotide orpolypeptide, refers to a polynucleotide or polypeptide that can vary inprimary, secondary, or tertiary structure, as compared to a referencepolynucleotide or polypeptide, respectively (e.g., as compared to awild-type polynucleotide or polypeptide). A “variant” of a HJVpolypeptide, for example SEQ ID NOs: 2, 3 or 4 is meant to refer to amolecule substantially similar in structure and function, i.e. where thefunction is the ability to increase serum iron levels in vivo and/ordecrease or inhibit hepcidin expression.

For example, a variant of an HJV peptide can contain a mutation ormodification that differs from a reference amino acid in SEQ ID NOs: 2,3, 4 or 5. In some embodiments, a variant of SEQ ID NOs: 2, 3, 4 or 5 isa fragment of SEQ ID NOs: 2, 3, 4 or 5 as disclosed herein. In someembodiments, a variant can be a different isoform of SEQ ID NOs: 2, 3, 4or 5 or can comprise different isomer amino acids. Variants can benaturally-occurring, synthetic, recombinant, or chemically modifiedpolynucleotides or polypeptides isolated or generated using methods wellknown in the art. Variants can include conservative or non-conservativeamino acid changes, as described below. Polynucleotide changes canresult in amino acid substitutions, additions, deletions, fusions andtruncations in the polypeptide encoded by the reference sequence.Variants can also include insertions, deletions or substitutions ofamino acids, including insertions and substitutions of amino acids andother molecules) that do not normally occur in the peptide sequence thatis the basis of the variant, for example but not limited to insertion ofornithine which do not normally occur in human proteins. The term“conservative substitution,” when describing a polypeptide, refers to achange in the amino acid composition of the polypeptide that does notsubstantially alter the polypeptide's activity. For example, aconservative substitution refers to substituting an amino acid residuefor a different amino acid residue that has similar chemical properties.Conservative amino acid substitutions include replacement of a leucinewith an isoleucine or valine, an aspartate with a glutamate, or athreonine with a serine. “Conservative amino acid substitutions” resultfrom replacing one amino acid with another having similar structuraland/or chemical properties, such as the replacement of a leucine with anisoleucine or valine, an aspartate with a glutamate, or a threonine witha serine. Thus, a “conservative substitution” of a particular amino acidsequence refers to substitution of those amino acids that are notcritical for polypeptide activity or substitution of amino acids withother amino acids having similar properties (e.g., acidic, basic,positively or negatively charged, polar or non-polar, etc.) such thatthe substitution of even critical amino acids does not reduce theactivity of the peptide, (i.e. the ability of the peptide to penetratethe BBB). Conservative substitution tables providing functionallysimilar amino acids are well known in the art. For example, thefollowing six groups each contain amino acids that are conservativesubstitutions for one another: 1) Alanine (A), Serine (S), Threonine(T); 2) Aspartic acid (D), Glutamic acid (E); 3) Asparagine (N),Glutamine (Q); 4) Arginine (R), Lysine (K); 5) Isoleucine (I), Leucine(L), Methionine (M), Valine (V); and 6) Phenylalanine (F), Tyrosine (Y),Tryptophan (W). (See also Creighton, Proteins, W. H. Freeman and Company(1984).) In some embodiments, individual substitutions, deletions oradditions that alter, add or delete a single amino acid or a smallpercentage of amino acids can also be considered “conservativesubstitutions” is the change does not reduce the activity of the peptide(i.e. the ability of an HJV peptide variant to increase serum iron invivo). Insertions or deletions are typically in the range of about 1 to5 amino acids. The choice of conservative amino acids may be selectedbased on the location of the amino acid to be substituted in thepeptide, for example if the amino acid is on the exterior of the peptideand expose to solvents, or on the interior and not exposed to solvents.

In alternative embodiments, one can select the amino acid which willsubstitute an existing amino acid based on the location of the existingamino acid, i.e. its exposure to solvents (i.e. if the amino acid isexposed to solvents or is present on the outer surface of the peptide orpolypeptide as compared to internally localized amino acids not exposedto solvents). Selection of such conservative amino acid substitutionsare well known in the art, for example as disclosed in Dordo et al, J.Mol Biol, 1999, 217, 721-739 and Taylor et al, J. Theor. Biol. 119(1986); 205-218 and S. French and B. Robson, J. Mol. Evol. 19 (1983)171.Accordingly, one can select conservative amino acid substitutionssuitable for amino acids on the exterior of a protein or peptide (i.e.amino acids exposed to a solvent), for example, but not limited to, thefollowing substitutions can be used: substitution of Y with F, T with Sor K, P with A, E with D or Q, N with D or G, R with K, G with N or A, Twith S or K, D with N or E, I with L or V, F with Y, S with T or A, Rwith K, G with N or A, K with R, A with S, K or P.

In alternative embodiments, one can also select conservative amino acidsubstitutions encompassed suitable for amino acids on the interior of aprotein or peptide, for example one can use suitable conservativesubstitutions for amino acids is on the interior of a protein or peptide(i.e. the amino acids are not exposed to a solvent), for example but notlimited to, one can use the following conservative substitutions: whereY is substituted with F, T with A or S, I with L or V, W with Y, M withL, N with D, G with A, T with A or S, D with N, I with L or V, F with Yor L, S with A or T and A with S, G, T or V. In some embodiments,non-conservative amino acid substitutions are also encompassed withinthe term of variants. A variant of a HJV peptide, for example a variantof SEQ ID NOs:2, 3, 4 or 5 is meant to refer to any moleculesubstantially similar in structure and function to either the entiremolecule of SEQ ID NOs:2, 3, 4 or 5, or to a fragment thereof.

The term “derivative” as used herein refers to peptides which have beenchemically modified, for example but not limited to by techniques suchas ubiquitination, labeling, pegylation (derivatization withpolyethylene glycol) or addition of other molecules. A molecule also a“derivative” of another molecule when it contains additional chemicalmoieties not normally a part of the molecule. Such moieties can improvethe molecule's solubility, absorption, biological half life, etc. Themoieties can alternatively decrease the toxicity of the molecule,eliminate or attenuate any undesirable side effect of the molecule, etc.Moieties capable of mediating such effects are disclosed in Remington'sPharmaceutical Sciences, 18th edition, A. R. Gennaro, Ed., MackPubl.,Easton, Pa. (1990).

The term “functional” when used in conjunction with “derivative” or“variant” refers to a molecule such as a protein which possess abiological activity (either functional or structural) that issubstantially similar to a biological activity of the entity or moleculeits is a functional derivative or functional variant thereof. The termfunctional derivative is intended to include the fragments, analogues orchemical derivatives of a molecule.

A molecule is said to be “substantially similar” to another molecule ifboth molecules have substantially similar structures or if bothmolecules possess a similar biological activity, for example if bothmolecules are able to increase serum iron in vivo and/or decrease orinhibit hepcidin expression. Thus, provided that two molecules possess asimilar activity, (i.e. a variant of an HJV peptide which can increaseserum iron concentration in vivo similar to that of the HJV peptidewhich corresponds to SEQ ID NOs: 2, 3, 4 or 5 when fused to Fc) areconsidered variants and are encompassed for use as disclosed herein,even if the structure of one of the molecules not found in the other, orif the sequence of amino acid residues is not identical. Thus, providedthat two molecules possess a similar biological activity, they areconsidered variants as that term is used herein even if the structure ofone of the molecules not found in the other, or if the sequence of aminoacid residues is not identical.

As used herein, the term “nonconservative” refers to substituting anamino acid residue for a different amino acid residue that has differentchemical properties. The nonconservative substitutions include, but arenot limited to aspartic acid (D) being replaced with glycine (G);asparagine (N) being replaced with lysine (K); or alanine (A) beingreplaced with arginine (R).

The term “insertions” or “deletions” are typically in the range of about1 to 5 amino acids. The variation allowed can be experimentallydetermined by producing the peptide synthetically while systematicallymaking insertions, deletions, or substitutions of nucleotides in thesequence using recombinant DNA techniques.

The term “substitution” when referring to a peptide, refers to a changein an amino acid for a different entity, for example another amino acidor amino-acid moiety. Substitutions can be conservative ornon-conservative substitutions.

The term “substantially similar”, when used to define a soluble form ofHJV, such as a HJV fusion protein comprising a functional variant of HJVor a functional derivative of HJV as compared to the HJV protein encodedby SEQ ID NOs: 2-5, means that a particular subject sequence, forexample, a HJV fragment or HJV variant or HJV derivative sequence,varies from the sequence of the natural (or wild-type) HJV protein (i.e.HJV encoded by SEQ ID NOs: 2, 3, 4 to 5), by one or more substitutions,deletions, or additions, although the net effect of which is to retainat least some of the biological activity found in the native natural HJVprotein. As such, nucleic acid and amino acid sequences having lesserdegrees of similarity but comparable biological activity to HJV areconsidered to be equivalents. In determining polynucleotide sequences,all subject polynucleotide sequences capable of encoding substantiallysimilar amino acid sequences are considered to be substantially similarto a reference polynucleotide sequence, regardless of differences incodon sequence. A nucleotide sequence is “substantially similar” to aspecific nucleic acid sequence of SEQ ID NOs:2 to 5 as disclosed hereinif: (a) the nucleotide sequence is hybridizes to the coding regions ofthe natural HJV, or (b) the nucleotide sequence is capable ofhybridization to nucleotide sequence of HJV encoded by SEQ ID NO:2 to 5under moderately stringent conditions and has biological activitysimilar to the native human HJV protein; or (c) the nucleotide sequenceswhich are degenerative as a result of the genetic code to the nucleotidesequences defined in (a) or (b). Substantially similar proteins willtypically be greater than about 80% similar to the correspondingsequence of the native protein.

The term “fragment” of a peptide or molecule as used herein refers toany contiguous polypeptide subset of the molecule. Fragments of an HJVpeptide, for example functional fragments of SEQ ID NOs: 2, 3, 4 or 5useful in the methods as disclosed herein have at least 30% of agonistor antagonist activity as that of SEQ ID NOs: 2, 3, 4 or 5. Statedanother way, a fragment of an HJV polypeptide is a fragment of any ofSEQ ID NOs: 2, 3, 4 or 5 which, when fused to Fc can result in at least30% of the same activity as compared to SEQ ID NOs: 1, 7 or 10 toincrease serum iron concentration and/or increase transferrin saturationwhen administered in a soluble form to a mouse in vivo (as disclosed inthe Examples and FIGS. 19 and 22 herein) and/or results in at least 30%of the activity as compared with SEQ ID NOs: 1, 7 or 10 to decreasebasal hepcidin expression in HepG cells in vitro or decreaseBMP-mediated induction of hepcidin expression using the BRE-luciferasein vitro assay as disclosed herein in the Examples and in FIGS. 17A-17D.It can also include fragments that decrease the wild type activity ofone property by at least 30%. Fragments as used herein are soluble (i.e.not membrane bound), and typically bound to a first fusion partner,however, they do not need to be fused to a fusion protein if the solubleHJV fragment is stable. A “fragment” can be at least about 6, at leastabout 9, at least about 15, at least about 20, at least about 30, leastabout 40, at least about 50, at least about 100, at least about 250, atleast about 500 nucleic or amino acids, and all integers in between.Exemplary fragments include C-terminal truncations, N-terminaltruncations, or truncations of both C- and N-terminals (e.g., deletionsof, for example, at least 1, at least 2, at least 3, at least 4, atleast 5, at least 8, at least 10, at least 15, at least 20, at least 25,at least 40, at least 50, at least 75, at least 100 or more amino acidsdeleted from the N-termini, the C-termini, or both). One of ordinaryskill in the art can create such fragments by simple deletion analysis.Such a fragment of SEQ ID NOs: 2 to 5 can be, for example, 1, 2, 3, 4,5, 6, 7, 8, 9 or 10 amino acids or more than 10 amino acids, such as 15,30, 50, 100 or more than 100 amino acids deleted from the N-terminaland/or C-terminal of SEQ ID NOs: 2 to 5, respectively. Persons ofordinary skill in the art can easily identify the minimal peptidefragment of SEQ ID NOs: 2 to 5 useful in the fusion proteins and methodsas disclosed herein, by sequentially deleting N- and/or C-terminal aminoacids from SEQ ID NOs: 2 to 5 and assessing the function of theresulting peptide fragment fused to a Fc fragment. One can createfunctional fragments with multiple smaller fragments. These can beattached by bridging peptide linkers. One can readily select linkers tomaintain wild type conformation. One of ordinary skill in the art caneasily assess the function of the HJV-fragment.Fc fusion protein toincrease serum iron concentration and/or increase transferrin saturationwhen administered to a mouse in vivo (as disclosed in the Examples andFIGS. 19 and 22 herein) as compared to HJV-Fc corresponding to SEQ IDNOs: 1, 7 or 10 as disclosed herein. Using such an in vivo assay, if theHJV-fragment.Fc protein has at least 30% of the biological activity ofthe HJV-Fc corresponding to SEQ ID NOs: 1, 7 or 10 as disclosed herein,then the HJV-fragment portion of the HJV-fragment.Fc protein isconsidered a valid HJV-fragment and can used in fusion proteins andmethods as disclosed herein. Alternatively, one of ordinary skill in theart can easily assess the function of the HJV-fragment.Fc fusion proteinby assessing its ability to decrease basal hepcidin expression in HepGcells in vitro as compared to HJV-Fc corresponding to SEQ ID NO: 1, 7 or10 as disclosed herein, or to determine the ability of theHJV-fragment.Fc protein to decrease BMP-mediated induction of hepcidinexpression using the BRE-luciferase in vitro assay as disclosed hereinin the Examples and in FIGS. 17A-17D. Using such an in vitro assay, ifthe HJV-fragment.Fc protein has at least 30% of the biological activityof the HJV-Fc corresponding to SEQ ID NO: 1, 7 or 10 as disclosedherein, then the HJV-fragment portion of the HJV-fragment.Fc protein isconsidered a valid HJV-fragment and can used in fusion proteins andmethods as disclosed herein. In some embodiments, a fragment of SEQ IDNOS: 2 to 5 can be less than 200, or less than 150 or less than 100, orless than 50, or less than 20 amino acids of SEQ ID NOS: 2, 3, 4 or 5.In some embodiments, a fragment of SEQ ID NOS: 2, 3, 4 or 5 is less than100 peptides in length. However, as stated above, the fragment must beat least 6 amino acids, at least about 9, at least about 15, at leastabout 20, at least about 30, at least about 40, at least about 50, atleast about 100, at least about 250, at least about 500 nucleic acids oramino acids, or any integers in between.

An “analog” of a molecule such as HJV peptide, for example SEQ ID NOs: 2to 5 refers to a molecule similar in function to either the entiremolecule or to a fragment thereof. The term “analog” is also intended toinclude allelic, species and induced variants. Analogs typically differfrom naturally occurring peptides at one or a few positions, often byvirtue of conservative substitutions. Analogs typically exhibit at least80 or 90% sequence identity with natural peptides. Some analogs alsoinclude unnatural amino acids or modifications of N or C terminal aminoacids. Examples of unnatural amino acids are, for example but notlimited to; acedisubstituted amino acids, N-alkyl amino acids, lacticacid, 4-hydroxyproline, γ-carboxyglutamate, ε-N,N,N-trimethyllysine,ε-N-acetyllysine, O-phosphoserine, N-acetylserine, N-formylmethionine,3-methylhistidine, 5-hydroxylysine, σ-N-methylarginine. Fragments andanalogs can be screened for prophylactic or therapeutic efficacy intransgenic animal models as described below.

By “covalently bonded” is meant joined either directly or indirectly(e.g., through a linker) by a covalent chemical bond.

The term “fusion protein” as used herein refers to a recombinant proteinof two or more proteins. Fusion proteins can be produced, for example,by a nucleic acid sequence encoding one protein is joined to the nucleicacid encoding another protein such that they constitute a singleopen-reading frame that can be translated in the cells into a singlepolypeptide harboring all the intended proteins. The order ofarrangement of the proteins can vary. As a non-limiting example, thenucleic acid sequence encoding the HJV fusion protein is derived fromthe nucleotide sequence of encoding a HJV protein or a functionalderivative fragment or variant thereof, fused in frame to an end, eitherthe 5′ or the 3′ end, of a gene encoding a first fusion partner, such asa IgG1 Fc fragment. In this manner, on expression of the gene, the HJVprotein or a functional derivative fragment or variant thereof isfunctionally expressed and fused to the N-terminal or C-terminal end ofthe IgG1 Fc. In certain embodiments, modification of the polypeptideprobe is such that the functionality of the HJV protein or a functionalderivative fragment or variant thereof remains substantially unaffectedin terms of its biological activity by fusion to the first fusionpartner, such as IgG1 Fc.

The terms “subject” and “individual” and “patient” are usedinterchangeably herein, and refer to an animal, for example a human ornon-human animal (e.g., a mammal), to whom treatment, includingprophylactic treatment, with a pharmaceutical composition as disclosedherein, is provided. The term “subject” as used herein refers to humanand non-human animals. The term “non-human animals” and “non-humanmammals” are used interchangeably herein and includes all vertebrates,e.g., mammals, such as non-human primates, (particularly higherprimates), sheep, dog, rodent (e.g. mouse or rat), guinea pig, goat,pig, cat, rabbits, cows, and non-mammals such as chickens, amphibians,reptiles etc. In one embodiment, the subject is human. In anotherembodiment, the subject is an experimental animal or animal substituteas a disease model.

“Treating” a disease or condition in a subject or “treating” a patienthaving a disease or condition refers to subjecting the individual to apharmaceutical treatment, e.g., the administration of a drug, such thatat least one symptom of the disease or condition is decreased,stabilized, or prevented.

By “specifically binds” or “specific binding” is meant a compound orantibody that recognizes and binds a desired polypeptide but that doesnot substantially recognize and bind other molecules in a sample, forexample, a biological sample, which naturally includes a polypeptide ofthe invention.

By “substantially pure” or is meant a nucleic acid, polypeptide, orother molecule that has been separated from the components thatnaturally accompany it. Typically, a polypeptide is substantially purewhen it is at least about 60%, or at least about 70%, at least about80%, at least about 90%, at least about 95%, or even at least about 99%,by weight, free from the proteins and naturally-occurring organicmolecules with which it is naturally associated. For example, asubstantially pure polypeptide may be obtained by extraction from anatural source, by expression of a recombinant nucleic acid in a cellthat does not normally express that protein, or by chemical synthesis.

By a “decrease” or “inhibition” used in the context of the level ofexpression or activity of a gene refers to a reduction in protein ornucleic acid level or activity in a cell, a cell extract, or a cellsupernatant. For example, such a decrease may be due to reduced RNAstability, transcription, or translation, increased protein degradation,or RNA interference. Preferably, this decrease is at least about 5%, atleast about 10%, at least about 25%, at least about 50%, at least about75%, at least about 80%, or even at least about 90% of the level ofexpression or activity under control conditions.

By an “increase” in the expression or activity of a gene or protein ismeant a positive change in protein or nucleic acid level or activity ina cell, a cell extract, or a cell supernatant. For example, such aincrease may be due to increased RNA stability, transcription, ortranslation, or decreased protein degradation. Preferably, this increaseis at least 5%, at least about 10%, at least about 25%, at least about50%, at least about 75%, at least about 80%, at least about 100%, atleast about 200%, or even about 500% or more over the level ofexpression or activity under control conditions.

By “enhanced proteolytic stability” is meant a reduction of in the rateor extent of proteolysis of a peptide sequence by at least about 2%, atleast about 5%, at least about 10%, at least about 20%, at least about30%, at least about 40%, at least about 50%, at least about 60%, atleast about 70%, at least about 80%, at least about 85%, at least about90%, at least about 95%, at least about 98%, or at least about 99% ascompared to a control sequence under the same conditions (e.g., in vivoor in an in vitro system such as in a cell or cell lysate). A peptidewith enhanced proteolytic stability may contain any modification, forexample, insertions, deletions, or point mutations which reduce oreliminate a site subject to proteolytic cleavage at a particular site.Sites of proteolytic cleavage may be identified based on known targetsequences or using computer software (e.g., software described byGasteiger et al., Protein Identification and Analysis Tools on theExPASy Server. In John M. Walker, ed. The Proteomics Protocols Handbook,Humana Press (2005)). Alternatively, proteolytic sites can be determinedexperimentally, for example, by Western blot for the protein followingexpression or incubation in a cellular system or cellular lysate,followed by sequencing of the identified fragments to determine cleavagesites.

The term “recombinant” as used herein to describe a nucleic acidmolecule, means a polynucleotide of genomic, cDNA, viral, semisynthetic,and/or synthetic origin, which, by virtue of its origin or manipulation,is not associated with all or a portion of the polynucleotide with whichit is associated in nature. The term recombinant as used with respect toa protein or polypeptide, means a polypeptide produced by expression ofa recombinant polynucleotide. The term recombinant as used with respectto a host cell means a host cell into which a recombinant polynucleotidehas been introduced. Recombinant is also used herein to refer to, withreference to material (e.g., a cell, a nucleic acid, a protein, or avector) that the material has been modified by the introduction of aheterologous material (e.g., a cell, a nucleic acid, a protein, or avector).

The term “vectors” refers to a nucleic acid molecule capable oftransporting another nucleic acid to which it has been linked; a plasmidis a species of the genus encompassed by “vector”. The term “vector”typically refers to a nucleic acid sequence containing an origin ofreplication and other entities necessary for replication and/ormaintenance in a host cell. Vectors capable of directing the expressionof genes and/or nucleic acid sequence to which they are operativelylinked are referred to herein as “expression vectors”. In general,expression vectors of utility are often in the form of “plasmids” whichrefer to circular double stranded DNA loops which, in their vector formare not bound to the chromosome, and typically comprise entities forstable or transient expression or the encoded DNA. Other expressionvectors can be used in the methods as disclosed herein for example, butare not limited to, plasmids, episomes, bacterial artificialchromosomes, yeast artificial chromosomes, bacteriophages or viralvectors, and such vectors can integrate into the host's genome orreplicate autonomously in the particular cell. A vector can be a DNA orRNA vector. Other forms of expression vectors known by those skilled inthe art which serve the equivalent functions can also be used, forexample self replicating extrachromosomal vectors or vectors whichintegrates into a host genome. Preferred vectors are those capable ofautonomous replication and/or expression of nucleic acids to which theyare linked. Vectors capable of directing the expression of genes towhich they are operatively linked are referred to herein as “expressionvectors”.

The term “viral vectors” refers to the use of viruses, orvirus-associated vectors as carriers of a nucleic acid construct into acell. Constructs may be integrated and packaged into non-replicating,defective viral genomes like Adenovirus, Adeno-associated virus (AAV),or Herpes simplex virus (HSV) or others, including reteroviral andlentiviral vectors, for infection or transduction into cells. The vectormay or may not be incorporated into the cell's genome. The constructsmay include viral sequences for transfection, if desired. Alternatively,the construct may be incorporated into vectors capable of episomalreplication, e.g EPV and EBV vectors.

By “iron-related disorder” is meant any disease or condition where ironlevels are altered (e.g., increased or decreased) from the levelstypically found in healthy individuals. Specific conditions aredescribed herein. Conditions associated with iron overload include bothprimary and secondary iron overload diseases, syndromes or disorders,including, but not limited to, hereditary hemochromatosis, porphyriacutanea tarda, hereditary spherocytosis, hyprochromic anemia,hysererythropoietic anemia (CDAI), faciogenital dysplasia (FGDY),Aarskog syndrome, atransferrinemia, sideroblastic anemia (SA),pyridoxine-responsive sidero-blastic anemia, and hemoglobinopathies suchas thalassemia and sickle cell. Some studies have suggested anassociation between iron metabolism disorders, such as thalassemia andhemochromatosis, and a number of disease states, such as type II(non-insulin dependent) diabetes mellitus and atherosclerosis (Matthewset al., J. Surg. Res., 1997, 73: 35-40; Tuomainen et al, Diabetes Care,1997, 20: 426-428).

Conditions associated with iron deficiency include anemia of chronicdisease, iron deficiency anemias, functional iron deficiency, andmicrocytic anemia. The term “anemia of chronic disease” refers to anyanemia that develops as a result of, for example, extended infection,inflammation, and neoplastic disorders. The anemia which develops isoften characterized by a shortened red blood cell life span andsequestration of iron in macrophages, which results in a decrease in theamount of iron available to make new red blood cells. Conditionsassociated with anemia of chronic disease include, but are not limitedto, chronic bacterial endocarditis, osteomyelitis, rheumatic fever,ulcerative colitis, and neoplastic disorders. Further conditions includeother diseases and disorders associated with infection, inflammation,and neoplasms, including, for example, inflammatory infections (e.g.,pulmonary abscess, tuberculosis), inflammatory noninfectious disorders(e.g., rheumatoid arthritis, systemic lupus erythrematosus, Crohn'sdisease, hepatitis, inflammatory bowel disease), and various cancers,tumors, and malignancies (e.g., carcinoma, sarcoma, lymphoma). Irondeficiency anemia may result from conditions such as pregnancy,menstruation, infancy and childhood, and blood loss due to injury.

Iron metabolism plays a role in a number of other diseases states,including cardiovascular disease, Alzheimer's disease, Parkinson'sdisease, and certain types of colo-rectal cancers (see, for example,Tuomainen et al., Circulation, 1997, 97: 1461-1466; McCord, Circulation,1991, 83: 1112-1114; Sullivan, J. Clin. Epidemiol., 1996, 49: 1345-1352;Smith et al., Proc. Nat. Acad. Sci. USA, 1997, 94: 9866-9868; Riedereret al, J. Neurochem., 1989, 512: 515-520; Knekt et al., Int. J. Cancer,1994, 56: 379-382).

The articles “a” and “an” are used herein to refer to one or to morethan one (i.e., to at least one) of the grammatical object of thearticle. By way of example, “an element” means one element or more thanone element.

Other than in the operating examples, or where otherwise indicated, allnumbers expressing quantities of ingredients or reaction conditions usedherein should be understood as modified in all instances by the term“about.” The term “about” when used in connection with percentages canmean±1%. The present invention is further explained in detail by thefollowing examples, but the scope of the invention should not be limitedthereto.

It should be understood that this invention is not limited to theparticular methodology, protocols, and reagents, etc., described hereinand as such can vary. The terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to limit thescope of the present invention, which is defined solely by the claims.Other features and advantages of the invention will be apparent from thefollowing Detailed Description, the drawings, and the claims.

I. General

a. Hemojuvelin

Hemojuvelin (also known as RGMc, HFE2) is a member of the RepulsiveGuidance Molecule (RGM) family, including RGMa and DRAGON (also known asRGMb) (Papanikolaou et al., 2004. Nat. Genet. 36:77-82, Monnier et al.,2002. Nature. 419:392-395; Samad et al., 2004. J. Neurosci.24:2027-2036). The inventors have recently demonstrated that like RGMaand DRAGON (Samad et al., 2005. J. Biol. Chem. 280:14122-14129; Babittet al., 2005. J. Biol. Chem. 280:29820-29827), hemojuvelin functions asa BMP co-receptor that binds directly to BMP-2 and BMP-4 and enhancescellular responses to BMP, but not TGF-β, ligands. Furthermore, BMP-2positively regulates hepcidin expression (Truksa et al., 2006. Proc.Natl. Acad. Sci. USA. 103:10289-10293), and hemojuvelin increaseshepcidin induction in response to BMP-2.

Like RGM family members RGMa and DRAGON, the inventors show thathemojuvelin is a coreceptor that enhances BMP signaling via theclassical BMP pathway involving BMP ligands, BMP receptors, and BMPreceptor-activated Smads. The RGM family is the first documented familyof BMP coreceptors. Although over 40 TGF-β superfamily ligands have beendescribed, only five type I receptors and seven type II receptors havebeen identified. Coreceptors therefore have an important regulatory rolefor many TGF-β superfamily members to help generate specificity and atight spatiotemporal coordination of these signals. The inventorsbelieve RGM family members increase the sensitivity of cells in whichthey are expressed to low levels of BMP ligand (Samad et al., J. Biol.Chem. 280, 14122-14129 (2005); Babitt et al., J. Biol. Chem. 280,29820-29827 (2005); Shi et al., Cell 113, 685-700 (2003)).

Hemojuvelin protein is expressed in the liver, where hepcidin isproduced (Krause et al., FEBS Lett. 480, 147-150 (2000); Park et al., J.Biol. Chem. 276, 7806-7810 (2001); Pigeon et al., J. Biol. Chem. 276,7811-7819 (2001)). Hepcidin levels are depressed in patients with HFE2mutations and Hfe2^(−/−) mice, suggesting that hemojuvelin is a positiveregulator of hepcidin expression (Papanikolaou et al., Nat. Genet. 36,77-82 (2004); Huang et al., J. Clin. Invest. 115, 2187-2191 (2005);Niederkofler et al., J. Clin. Invest. 115, 2180-2186 (2005)). Hfe2^(−/−)mice also have markedly elevated intestinal and tissue macrophageferroportin expression, presumably owing to low hepcidin levels. Here,direct experimental evidence that hemojuvelin positively regulateshepcidin expression in liver cells is provided and that hemojuvelinmutants associated with juvenile hemochromatosis have an impairedability to upregulate hepcidin (Papanikolaou et al., Nat. Genet. 36,77-82 (2004); Lanzara et al., Blood 103, 4317-4321 (2004); Lee et al.,Blood 103, 4669-4671 (2004)). These hemojuvelin mutants also showimpaired BMP signaling in liver cells compared with wild-typehemojuvelin. This demonstrates that hemojuvelin's ability to function asa BMP coreceptor may be integral for its role in regulating hepcidinexpression and thereby systemic iron homeostasis.

Hemojuvelin expression in the liver is not uniform, as demonstrated inHfe2 mutant mice expressing lacZ from the Hfe2 locus. In these mice,lacZ activity is restricted to hepatocytes surrounding portal tracts butis not present in other hepatocytes or in other cell types that comprise30-40% of the liver, including Kupffer cells, stellate cells andsinusoidal endothelial cells (Niederkofler et al., J. Clin. Invest. 115,2180-2186 (2005); Alpini et al., Hepatology 20, 494-514 (1994)). Rgmaand Rgmb mRNA have also been detected in the rodent liver by RNA blot(Babitt et al., J. Biol. Chem. 280, 29820-29827 (2005)). It is possiblethat the cell type distribution of other RGM family members within theliver is different from hemojuvelin. For example, in the CNS, Rgma andRgmb mRNA are expressed predominantly in nonoverlapping areas and seemto have different physiologic roles (Samad et al., J. Neurosci. 24,2027-2036 (2004); Niederkofler et al., J. Neurosci. 24, 808-818 (2004);Monnier et al., Nature 419, 392-395 (2002); Rajagopalan et al. Nat. CellBiol. 6, 756-762 (2004); Matsunaga et al., Nat. Cell Biol. 6, 749-755(2004)). Alternatively, it is possible that hemojuvelin, but not otherRGM family members, may interact with other molecules involved inregulating hepcidin expression and iron metabolism.

Hemojuvelin is also highly expressed in skeletal and cardiac muscle(Papanikolaou et al., Nat. Genet. 36, 77-82 (2004); Samad et al., J.Neurosci. 24, 2027-2036 (2004); Niederkofler et al., J. Neurosci. 24,808-818 (2004); Rodriguez et al., Haematologica 89, 1441-1445 (2004)).Recent data suggest that human sera contains soluble hemojuvelin andthat soluble hemojuvelin can inhibit the expression of hepcidin mRNA(Lin et al., Blood 106, 2884-2889 (2005)). Hemojuvelin in muscle mayserve as a source of soluble hemojuvelin to regulate hepcidin expression(Lin et al., Blood 106, 2884-2889 (2005); Zhang et al., J. Biol. Chem.280, 33885-33894 (2005)). Thus, whereas cell-surface hemojuvelin in theliver acts as a BMP coreceptor to enhance cellular responses to BMPligands and increase hepcidin expression, soluble hemojuvelin may bindand sequester BMP ligands to inhibit both BMP signaling and hepcidinexpression. Both soluble DRAGON.Fc24 and RGMa.Fc fusion proteins inhibitthe biological activity of BMP ligands (data not shown). Hemojuvelin mayalso have a role in intracellular iron homeostasis, as overexpression ofhemojuvelin and neogenin in vitro increases intracellular ironaccumulation.

The inventors demonstrate herein that hemojuvelin is a novel BMPcoreceptor whose enhancement of BMP signaling is important in regulatinghepcidin expression and iron metabolism. Therapeutic strategiestargeting the BMP signaling pathway may therefore have a role intreating disorders of iron homeostasis, such as hemochromatosis andanemia of chronic disease.

Recently, mutations in the gene encoding hemojuvelin were identified asthe leading cause of juvenile hemochromatosis, resulting in a phenotypeindistinguishable from hemochromatosis due to HAMP mutations. Humanswith HFE2 mutations and Hfe2^(−/−) mice have low hepcidin levels, andsiRNA inhibition of HFE2 decreases hepcidin expression in vitro,suggesting that hemojuvelin positively regulates hepcidin expression. Amember of the RGM family, hemojuvelin shares 50-60% amino acid identityand key structural features with RGMa and DRAGON(RGMb), including anN-terminal signal sequence, proteolytic cleavage site, partial vonWillebrand factor type D domain and glycophosphatidylinositol (GPI)anchor.

Hemojuvelin mutants associated with juvenile hemochromatosis haveimpaired BMP signaling ability, and hepatocytes from Hfe2^(−/−) micedemonstrate blunted hepcidin induction in response to BMP-2 (describedherein and in Babitt et al., 2006. Nat. Genet. 38:531-539). Thissuggests that the mechanism for iron overload in patients withhemojuvelin mutations is due to decreased BMP signaling in the liverleading to decreased hepcidin expression.

b. BMP/TGF-β Superfamily

BMPs represent a large subfamily of the transforming growth factor β(TGF-β) superfamily of ligands, which share a common model of signaltransduction (Shi et al., Cell 113, 685-700 (2003)). Signaling isinitiated when ligand binds to complexes of two type I and two type IIserine/threonine kinase receptors. Constitutively active type IIreceptors phosphorylate type I receptors, which phosphorylate Smadproteins. The BMP subfamily signals via one set of receptor-activatedSmads (Smad1, Smad5 and Smad8), whereas the TGF-β subfamily signals viaanother set (Smad2 and Smad3). Phosphorylated receptor-activated Smadsform heteromeric complexes with common mediator Smad4, and the Smadcomplexes translocate to the nucleus where they modulate genetranscription. Regulation of this pathway occurs at multiple levels inorder to generate specificity and to finely tune these signals. One keyregulatory mechanism is the promotion or inhibition of ligand binding bycoreceptors. RGM family members RGMa and DRAGON are the first describedcoreceptors for the BMP subfamily. Both RGMa and DRAGON bind selectivelyto BMP-2 and BMP-4 ligands, interact with BMP receptors and enhancecellular responses to BMP ligands (Samad et al., J. Biol. Chem. 280,14122-14129 (2005); Babitt et al., J. Biol. Chem. 280, 29820-29827(2005); Shi et al., Cell 113, 685-700 (2003)).

BMPs have diverse roles in many physiologic and pathologic processes,including cell proliferation, differentiation and apoptosis (Hogan etal, Genes Dev. 10, 1580-1594 (1996); Zhao et al., Genesis 35, 43-56(2003); Balemans et al., Dev. Biol. 250, 231-250 (2002)). Recently, alink between TGF-β superfamily signaling and iron metabolism wasdiscovered: mice with a liver-specific conditional knockout of Smad4were found to have reduced hepatic hepcidin expression and total bodyiron overload (Wang et al., Cell Metab. 2, 399-409 (2005)). Here, theinventors show that hemojuvelin is a BMP coreceptor and that byenhancing BMP signaling, hemojuvelin has a role in systemic ironmetabolism through regulation of hepcidin expression.

Members of the BMP/TGF-β superfamily, which include BMPs, TGF-βs, growthand differentiation factors (GDFs), and Activins, initiate anintracellular signaling cascade by binding to a complex of type I andtype II serine threonine kinase receptors (Shi et al., 2003. Cell. 113,685-700). The activated receptor complex phosphorylates intracellularSmad proteins, which then complex with common-mediator Smad4. Smadcomplexes translocate to the nucleus where they modulate genetranscription. In general, BMPs and GDFs signal via one set of Smadproteins (1, 5, and 8), while TGF-βs and Activins signal via another set(Smad2 and Smad3).

A link between BMP/TGF-β signaling, hepcidin expression and ironmetabolism in vivo is supported by the recent description of a mousewith a liver-specific conditional knockout of Smad4, encoding the commondownstream mediator for all TGF-β superfamily ligands. These mice havereduced hepatic hepcidin expression and total body iron overload (Wanget al., Cell Metab. 2, 399-409 (2005)). Here, the inventors show thatBMP-2 positively regulates hepcidin expression at the transcriptionallevel. the inventors also demonstrate that hemojuvelin enhances hepcidininduction in response to BMP-2 and that Hfe2^(−/−) hepatocytes show asignificantly reduced induction of hepcidin expression in response toBMP-2. Furthermore, livers of Hfe2^(−/−) mice have reduced levels ofphosphorylated Smad1/5/8, indicating that the absence of hemojuvelinresults in lower hepatic BMP signaling in vivo. The inventors thereforepropose that hemojuvelin-mediated BMP signaling is an importantmechanism for regulating hepcidin expression and iron homeostasis (FIG.1). Loss of hemojuvelin function leads to decreased BMP signaling inliver cells, which then decreases hepcidin expression. Impairedregulation by hepcidin leads to ferroportin overactivity, therebyresulting in increased intestinal iron absorption, increased macrophageiron release, elevated serum iron, and abnormal tissue iron deposition.

Hfe2^(−/−) hepatocytes do maintain some induction of hepcidin expressionin response to exogenous BMP-2. The inventors believe that under normalphysiologic conditions, the liver expresses a low endogenous level ofBMP ligand and that hemojuvelin serves to sensitize the cells to thislow level of BMP ligand. Under these conditions, hemojuvelin is requiredto generate sufficient intracellular BMP signals to produce hepcidin.Under conditions of exposure to high levels of exogenous BMP ligands,the large excess of BMP ligand can bypass the requirement forhemojuvelin to generate sufficient intracellular BMP signals via BMPtype I and type II receptors to stimulate hepcidin production.

Many BMP and TGF-β superfamily ligands are expressed endogenously in theadult liver (De Bleser et al., J. Hepatol. 26, 886-893 (1997); Kingsleyet al., Trends Genet. 10, 16-21 (1994); Knittel et al., Exp. Cell Res.232, 263-269 (1997); Miller et al., J. Biol. Chem. 275, 17937-17945(2000)). As disclosed herein, the inventors findings demonstrate thathemojuvelin binds preferentially to BMP-2 and, to a lesser extent,BMP-4, but further work will be needed to definitively determine theendogenous BMP/TGF-β superfamily ligand(s) through which hemojuvelinregulates hepatic hepcidin expression in vivo. Both BMP-4 and TGF-β1 canincrease hepatic hepcidin mRNA expression in vitro (Wang et al., CellMetab. 2, 399-409 (2005)). However, data suggest that the TGF-βsubfamily might be less critical than the BMP subfamily for positivelyregulating hepcidin expression in vivo, as livers of TGF-βreceptor-activated Smad3^(−/−) mice do not show any evidence of ironoverload (Wang et al. Cell Metab. 2, 399-409 (2005)), and transgenichepatic expression of a dominant-negative TGF-β type II receptor in micedoes not result in any obvious liver abnormalities (Kanzler et al.,Oncogene 20, 5015-5024 (2001)).

In addition to the BMP/TGF-β superfamily signaling pathway and ironstatus, inflammatory mediators also modulate hepcidin expression (Pigeonet al., J. Biol. Chem. 276, 7811-7819 (2001); Nicolas et al., J. Clin.Invest. 110, 1037-1044 (2002); Lee et al., Proc. Natl. Acad. Sci. USA102, 1906-1910 (2005); Nemeth et al., Blood 101, 2461-2463 (2003);Nemeth et al., J. Clin. Invest. 113, 1271-1276 (2004)). Mice lackinghemojuvelin robustly upregulate hepcidin expression in response tolipopolysaccharide or interleukin-6 (IL-6; Niederkofler et al., J. Clin.Invest. 115, 2180-2186 (2005)). Further, suppression of hemojuvelinexpression with small interfering RNA (siRNA) in Hep3B cells does notaffect IL-6 induction of hepcidin expression. As disclosed herein, thesedata suggest that inflammatory mediators act independently ofhemojuvelin to regulate hepcidin. Mice with a liver-specific knockout ofSmad4 demonstrate attenuated induction of hepcidin expression inresponse to IL-6 (Wang et al. Cell Metab. 2, 399-409 (2005)).Additionally, soluble hemojuvelin inhibits induction of hepcidin mRNAexpression by IL-6. Inflammatory stimuli have also been noted todecrease transcription of Hfe2 mRNA in wild-type mice. Thus there is acomplex interplay between the inflammatory pathway, the BMP/TGF-βsignaling pathway, and hemojuvelin (Niederkofler et al., J. Clin.Invest. 115, 2180-2186 (2005); Lin et al., Blood 106, 2884-2889 (2005);Wang et al., Cell Metab. 2, 399-409 (2005); Krijt et al., Blood 104,4308-4310 (2004)).

Further evidence supporting a role for BMP signaling in regulatinghepcidin expression and iron metabolism in vivo comes from mice with aconditional liver-specific knockout of Smad4. These mice have lowhepcidin levels and develop iron overload. In that study, both BMP-4 andTGF-β1 induce hepcidin expression in liver cells in vitro (Wang et al.,2005. Cell Metab. 2:399-409). Hepcidin induction by BMP-9 has also beendescribed (Truksa et al., 2006. Proc. Natl. Acad. Sci. USA.103:10289-10293). Indeed, many superfamily members are endogenouslyexpressed in the liver, including BMP-2, BMP-4, BMP-5, BMP-6, BMP-9, andall 3 TGF-β ligands (De Bleser et al., 1997. J. Hepatol. 26:886-893;Kingsley, 1994. Trends Genet. 10:16-21; Knittel et al., 1997. Exp. CellRes. 232:263-269; Su et al., 2002. Proc. Natl. Acad. Sci. USA.99:4465-4470; Miller et al., 2000. J. Biol. Chem. 275:17937-17945 anddata not shown). Data showing that hemojuvelin is a BMP co-receptor, butinvolved in not TGF-β signaling, suggests that members of the BMPsubfamily are more important than members of the TGF-β subfamily forregulating iron metabolism in vivo. Here, the inventors show that manymembers of the TGF-β superfamily can induce hepcidin mRNA expression invitro. However, a subset of BMP ligands, including BMP-2, BMP-4, BMP-5,BMP-6, BMP-7, and BMP-9 are much more potent inducers of hepcidinexpression than other ligands tested, including all three TGF-β ligands.Three-fold induction of hepcidin expression by TGF-β1 is consistent withprior findings (Wang et al., 2005. Cell Metab. 2:399-409); however,BMP-4 and BMP-9 were much more potent inducers of hepcidin expressioncompared with prior studies (Wang et al., 2005. Cell Metab. 2:399-409;Truksa et al., 2006. Proc. Natl. Acad. Sci. USA. 103:10289-10293). Thismay be related to differences in ligand concentration (2 to 5-foldhigher in our study) or differences in cell lines. Although BMP-9 isexpressed in the liver (Miller et al., 2000. J. Biol. Chem.275:17937-17945) and robustly increased hepcidin mRNA expression invitro, HJV.Fc was unable to inhibit BMP-9 activation of the hepcidinpromoter. HJV.Fc also has a reduced ability to inhibit BMP-7 as comparedwith BMP-2, -4, -5, and -6 ligands. The ability of HJV.Fc to inhibithepcidin expression and increase serum iron in vivo indicates thatBMP-2, BMP-4, BMP-5, and/or BMP-6 are good candidates for endogenousregulators of hepcidin expression, while BMP-9, BMP-7, and TGF-β ligandsmay be less important endogenous regulators of hepcidin.

Inhibition of hepatic BMP signaling may be the predominant mechanism bywhich HJV.Fc inhibits hepcidin expression and regulates systemic ironbalance in vivo. Indeed, inhibition of endogenous BMP signaling in HepG2cells using BMP siRNAs had a similar effect on decreasing hepcidinexpression as treatment with HJV.Fc. Further, loss of TGF-β/BMPsuperfamily signaling in the liver is sufficient to reduce hepcidinexpression and generate iron overload, as shown in mice with aliver-specific conditional knockout of Smad4 (Wang et al., 2005. CellMetab. 2:399-409). However, HJV has been shown to bind to the receptorneogenin, a member of the Deleted in Colon Cancer (DCC) receptor group,which has been reported to have a role in diverse functions includingcell survival, axonal guidance, and cellular iron uptake (Zhang et al.,2005. J. Biol. Chem. 280:33885-33894). Treatment with HJV.Fc in ourstudy did not appear to have any other adverse effects on mice. Indeed,regulation of hepcidin expression and iron metabolism appears to be theprincipal role for TGF-β/BMP superfamily signaling in the adult liver invivo, since iron overload was the predominant phenotype ofliver-specific conditional Smad4 knockout mice (Wang et al., 2005. CellMetab. 2:399-409).

c. Iron Homeostatis

Iron homeostasis is tightly regulated to provide this critical elementfor growth and survival while preventing the toxicity of iron excess.Plasma iron levels are maintained by intestinal absorption,reticuloendothelial cell recycling and mobilization of hepatocytestores. Circulating iron is loaded onto serum transferrin and deliveredprimarily to the bone marrow for erythropoiesis. Sloughing ofenterocytes and blood loss are the only significant means for removingexcess iron from the body; the remaining iron is stored primarily inhepatocytes and macrophages (Hentze et al., Cell 117, 285-297 (2004)).

As there is no known regulated mechanism for iron excretion, systemiciron homeostasis is maintained by tight regulation of intestinal ironabsorption and macrophage and hepatocyte iron release. Although themechanism for this remains to be fully elucidated, hepcidin seems tohave a key role. A soluble protein secreted by the liver (Krause et al.,FEBS Lett. 480, 147-150 (2000); Park et al., J. Biol. Chem. 276,7806-7810 (2001); Pigeon et al., J. Biol. Chem. 276, 7811-7819 (2001)),hepcidin promotes internalization and degradation of ferroportin, aniron exporter located on the surface of enterocytes, macrophages andhepatocytes (Nemeth et al., Science 306, 2090-2093 (2004)). Hepcidinthereby decreases both intestinal iron absorption and macrophage ironrelease. Mice lacking hepcidin expression and humans with mutations inthe hepcidin gene (HAMP) have been found to develop severe iron overloadat an early age, thus defining the first discovered cause of juvenilehemochromatosis (Nicolas et al., Proc. Natl. Acad. Sci. USA 98,8780-8785 (2001); Roetto et al., Nat. Genet. 33, 21-22 (2003)). Datasuggest that hepcidin expression is enhanced by iron overload andinflammation (Pigeon et al., J. Biol. Chem. 276, 7811-7819 (2001);Nicolas et al., J. Clin. Invest. 110, 1037-1044 (2002); Lee et al.,Proc. Natl. Acad. Sci. USA 102, 1906-1910 (2005); Nemeth et al., Blood101, 2461-2463 (2003); Nemeth et al., J. Clin. Invest. 113, 1271-1276(2004)), whereas it is inhibited by anemia and hypoxia. This isconsistent with a compensatory role for hepcidin to limit intestinalabsorption during iron overload and to increase iron availability whenneeded for erythropoiesis.

Hepcidin deficiency is the common pathogenic mechanism for both juvenileand adult forms of the genetic iron overload disorder hereditaryhemochromatosis, due to mutations in HAMP, HFE2, TFR2, and HFE(Pietrangelo, 2006. Biochim Biophys Acta. 1763:700-710; Roetto et al.,2003. Nat. Genet. 33:21-22; Papanikolaou et al., 2004. Nat. Genet.36:77-82; Huang et al., 2005. J. Clin. Invest. 115:2187-2191;Niederkofle et al., 2005. J. Clin. Invest. 115:2180-2186; Ahmad et al.,2002. Blood Cells Mol. Dis. 29:361-366; Bridle et al., 2003. Lancet.361:669-673; Muckenthaler et al., 2003. Nat. Genet. 34:102-107; Nicolaset al., 2003. Nat. Genet. 34:97-101; Kawabata et al., 2005. Blood.105:376-381; Nemeth et al., 2005. Blood. 105:1803-1806). As describedbelow, hemojuvelin acts as a co-receptor for BMP signaling and thatBMP-2 signaling induces hepcidin expression in vitro. As shown herein,BMP-2 administration in mice increases hepcidin expression and reducesserum iron levels in vivo. The modest induction of hepcidin expressionin response to BMP-2 in vivo compared to the in vitro data is likelymultifactorial. First, the mice were maintained on a standard diet,where dietary iron is replete, basal hepcidin levels are generally high,and hepcidin induction by well-established regulators such as iron andLPS have been reported to be absent or less robust compared with micemaintained on an iron-deficient diet (Nemeth et al., 2004. J. Clin.Invest. 113:1271-1276). Indeed, the degree of hepcidin induction byBMP-2 in our study was similar to the 1.8-fold induction reported afterLPS administration in mice fed on a standard diet (Roy et al., 2004.Nat. Genet. 36:481-485). BMPs typically act in an autocrine or paracrinefashion in vivo, while intravenously administered BMP-2 is rapidlyeliminated from the systemic circulation (t_(1/2)=16 minutes) (SeeSummary of Safety and Effectiveness data for INFUSE# Bone Graft, WyethPharmaceuticals, Inc, which is available athttp://www.fda.gov/cdrh/PDF4/p000054b.pdf). Thus, the systemicallyadministered BMP-2 dose may not be efficiently delivered to the liver.Nevertheless, the decrease in serum iron suggests that the BMP-2-inducedincrease in hepcidin expression was physiologically relevant, and theinventors believe reflects decreased iron export fromreticuloendothelial cells and duodenal enterocytes due tohepcidin-induced internalization and degradation of ferroportin.Although systemic BMP-2 treatment may be impractical due to high costand rapid elimination from the systemic circulation, therapies whichenhance hepatic BMP signaling may provide alternative treatmentstrategies for managing iron overload in patients with hereditaryhemochromatosis.

d. Anemia

Anemia of chronic disease, also known as anemia of inflammation, isprevalent in patients with many systemic diseases including autoimmunedisorders, malignancy, and chronic kidney disease (Weiss et al., 2005.N. Engl. J. Med. 352:1011-1023). In these patients, intestinal ironabsorption is impaired and iron remains sequestered inreticuloendothelial cells, leading to hypoferremia and anemia (Weiss etal., 2005. N. Engl. J. Med. 352:1011-1023). Research over the lastseveral years implicates hepcidin excess in the pathogenesis of thisdisease (Weiss et al., 2005. N. Engl. J. Med. 352:1011-1023; Pigeon etal., 2001. J. Biol. Chem. 276:7811-7819; Nicolas et al., 2002. J. Clin.Invest. 110:1037-1044, Nemeth et al., 2004. J. Clin. Invest.113:1271-1276, Nemeth et al., 2003. Blood. 101:2461-2463, Lee et al.,2005. Proc. Natl. Acad. Sci. USA. 102:1906-1910). A key regulator ofsystemic iron homeostasis (Hentze et al., 2004. Cell. 117:285-297),hepcidin is secreted by the liver (Pigeon et al., 2001. J. Biol. Chem.276:7811-7819; Krause et al., 2000. FEBS Lett. 480:147-150; Park et al.,2001. J. Biol. Chem. 276:7806-7810) and induces internalization anddegradation of the iron exporter ferroportin in absorptive enterocytesand reticuloendothelial cells, thereby inhibiting iron absorption fromthe intestine and iron release from reticuloendothelial cell stores(Nemeth et al., 2004. Science. 306:2090-2093). Hepcidin expression isinhibited by anemia and hypoxia, thus increasing iron availability whenneeded for erythropoiesis (Nicolas et al., 2002. J. Clin. Invest.110:1037-1044). Conversely, hepcidin expression is induced by ironloading, thus providing a feedback mechanism to limit further ironabsorption (Pigeon et al., 2001. J. Biol. Chem. 276:7811-7819; Nicolaset al., 2002. J. Clin. Invest. 110:1037-1044; Nemeth et al., 2004. J.Clin. Invest. 113:1271-1276). Hepcidin expression is also induced byinflammatory cytokines, and this is thought to be the mechanismunderlying the impaired intestinal iron absorption, reticuloendothelialcell iron sequestration, and hypoferremia characteristic of anemia ofchronic disease (Weiss et al., 2005. N. Engl. J. Med. 352:1011-1023;Pigeon et al., 2001. J. Biol. Chem. 276:7811-7819; Nicolas et al., 2002.J. Clin. Invest. 110:1037-1044; Nemeth et al., 2004. J. Clin. Invest.113:1271-1276; Nemeth et al., 2003. Blood. 101:2461-2463; Lee et al.,2005. Proc. Natl. Acad. Sci. USA. 102:1906-1910).

While hepcidin excess has a role in anemia of chronic disease,inadequate hepcidin expression appears to be a common pathogenicmechanism for the iron overload disorder hereditary hemochromatosis, dueto mutations in the genes encoding hepcidin (HAMP), hemojuvelin (HFE2),HFE, or Transferrin receptor 2 (TFR2). In patients and animal modelswith iron overload due to mutations in these genes, hepcidin levels arelow, thereby leading to ferroportin overactivity, increased intestinaliron absorption, increased reticuloendothelial cell iron release,elevated serum iron levels, and abnormal tissue iron deposition(Pietrangelo, 2006. Biochim Biophys Acta. 1763:700-710; Roetto et al.,2003. Nat. Genet. 33:21-22; Papanikolaou et al., 2004. Nat. Genet.36:77-82; Huang et al., 2005. J. Clin. Invest. 115:2187-2191;Niederkofle et al., 2005. J. Clin. Invest. 115:2180-2186; Ahmad et al.,2002. Blood Cells Mol. Dis. 29:361-366; Bridle et al., 2003. Lancet.361:669-673; Muckenthaler et al., 2003. Nat. Genet. 34:102-107; Nicolaset al., 2003. Nat. Genet. 34:97-101; Kawabata et al., 2005. Blood.105:376-381; Nemeth et al., 2005. Blood. 105:1803-1806). Evidencesuggests that hemojuvelin functions as a coreceptor for bonemorphogenetic protein (BMP) signaling, and that BMP/TGF-β superfamilysignaling has a role in regulating hepcidin expression and systemic ironbalance (Wang et al., 2005. Cell Metab. 2:399-409; Truksa et al., 2006.Proc. Natl. Acad. Sci. USA. 103:10289-10293).

Anemia of chronic disease is associated with hypoferremia andreticuloendothelial cell iron sequestration. Inflammatory cytokines arepotent inducers of hepcidin expression, and hepcidin excess may play akey role in the pathogenesis of anemia in these patients (Weiss et al.,2005. N. Engl. J. Med. 352:1011-1023; Pigeon et al., 2001. J. Biol.Chem. 276:7811-7819; Nicolas et al., 2002. J. Clin. Invest.110:1037-1044; Nemeth et al., 2004. J. Clin. Invest. 113:1271-1276;Nemeth et al., 2003. Blood. 101:2461-2463; Lee et al., 2005. Proc. Natl.Acad. Sci. USA. 102:1906-1910). Presumably, inhibitors of hepcidinexpression would allow for increased availability of iron from the dietand increased mobilization of iron from the spleen, thereby improvingred blood cell production and ameliorating anemia. The data presentedherein provide in vivo evidence that soluble HJV.Fc inhibits BMPsignaling in the liver, inhibits hepcidin expression, increasesferroportin protein expression, decreases splenic iron stores, andincrease serum iron levels. As described in detail below, HJV.Fc is thusa potential new treatment for anemia associated with hepcidin excess.

e. Other Mediators of Hepcidin Expression

Inflammatory mediators such as IL-6 may regulate hepcidin expressionthrough STAT3 (Wrighting et al., 2006. Blood. 108:3204-3209; VergaFalzacappa et al., 2007. Blood. 109:353-358; Pietrangelo et al., 2007.Gastroenterology. 132:294-300). Mice with a liver specific conditionalknockout of Smad4 demonstrate attenuated hepcidin induction in responseto IL-6 (Wang et al., 2005. Cell Metab. 2:399-409). This demonstratesthat BMP/TGF-β superfamily signaling is necessary for hepcidin excess ininflammatory states, and that inhibition of BMP signaling with HJV.Fcattenuates this hepcidin excess. As shown below, HJV.Fc inhibitshepcidin induction in response to the inflammatory cytokine IL-6,consistent with prior reports for recombinant soluble hemojuvelin (Linet al., 2005. Blood. 106:2884-2889). Taken together, HJV.Fc, or otherinhibitors of BMP signaling, can provide treatments for anemia ofchronic disease caused by inflammation.

II. HJV Polypeptides, Derivative and Fragments

Human hemojuvelin (HJV) has five predicted spliced transcripts encodingthree different proteins of 426, 313 and 200 amino acids (correspondingto SEQ ID NOs: 2, 3, and 4 respectively). HJV is also commonly known inthe art by the following alternative names; JH, HFE2A, RGMc, HJV, andHFE2. HJV possess multiple protein domains, including a hydrophobicN-terminal signal peptide, a conserved RGD triamino motif, a partial vonWillbrandt factor D motif, and a C-terminal glycoylphosphatidylinisotol(GPI) membrane anchor domain (Papanikolaou et al, 2004; Nat Genetics,36; 77-82). HJV shares considerable sequence identity to other RGMfamily members (see FIG. 23 and Papanikolaou et al, 2004; Nat Genetics,36; 77-82), and human HJV is the orthologue to rRGMc (see FIG. 24). HJVcan undergo autocleavage at a conserved Asp-Pro bond (residues 172-173in human HJV), resulting in two fragments held together by a disulfidebond (Zhang et al, 2005; JBC, 280; 338885-94; Lin et al, 2005; blood,106; 2884-89).

Phylogenetic analysis of HJV homologue sequences indicates a pattern ofconserved residues (see Carnus et al, J Mol Evol, 2007; 65; 68-81, whichis incorporated in its entirety herein by reference). Analysis of thefull length human HJV indicates 7 regions (regions 1-7), a N-terminalSignal peptide (residues 1-35), and a propeptide (residues 401-426) (seeFIG. 4 in Carnus et al, J Mol Evol, 2007; 65; 68-81). Regions 1, 3 and 5have been identified as conserved regions, which correspond to aminoacids 35-50 (region 1), 80-125 (region 3) and 167-267 (region 5) onhuman HJV. Residues for Region 1-7 classification are based on human HJVsequence GenBank Accession No. Q6ZVN8 (SEQ ID NO: 61).

Region 1 (residues 35-50) of HJV is a N-terminal conserved region ofabout 15 amino acids long comprising two conserved cysteine residues.Region 2 (residues 51-79) of HJV is variable but comprises a number ofglycine residues for enhanced stability and several helical regions aswell as structural flexibility (Carnus et al, J Mol Evol, 2007; 65;68-81). Region 3 (residues 80-125) of HJV is a conserved regioncomprising a RGM motif (residues 98-100) which is predicted to be on thesurface of the protein and may play a role in cell attachment orrecognition signal for certain ligands or signal transduction, possiblyin iron homeostasis (Collin et al, 2006; Biol Res, 39; 25-37).

Region 4 (residues 126-166) is a variable region except for a short CXYmotif beginning at 148, with conserved residues 165 and 166 beingconserved as either LH, TH or LF among different species HJV homologues.Region 5 (residues 167-256) is a conserved region comprising threecysteine residues and other structural motifs and a potentialglycosylation site and a partial van Willebrand D motif (VWD: 167-310).This region also contains highly conserved mutations, such as F170 andD172E, which are associated with iron overload (De Gobbi et al, 2002, BrJ Haematol 117:973-979), which are near the FGDPHL motif and the G250Vmutation which leads to iron overload (De Gobbi et al, 2002, Br JHaematol 117:973-979). Region 6 (residues 257-256), comprises predictedβ-sheets and two conserved cysteines, as well as known mutations inhuman HJV, C282Y (Feder et al., 1998, Proc Natl Acc Sci, USA, 95;1472-77) and G320V, which is in a conserved motif, LCVXGCP (Rivard etal, 2003; Eur J Hum Genet 11; 585-589).

In one embodiment, a HJV fusion polypeptide useful in the compositionsand methods as disclosed herein comprises a human HJV polypeptide and afirst fusion partner. In one embodiment, the HJV fusion polypeptideconsists essentially of a human HJV polypeptide and a first fusionpartner. In one embodiment, the HJV fusion polypeptide consists of ahuman HJV polypeptide and a first fusion partner.

In another embodiment, the HJV fusion polypeptide comprises human HJVpolypeptide which comprises, or alternatively, consists of a polypeptidehaving the sequence of SEQ ID NO: 2 or 3, or 4, or a functional fragmentthereof, or a HJV functional fragment of SEQ ID NO: 7 or 10. In anotherembodiment, the nucleic acid construct comprises a polypeptide encodedby the sequence corresponding to SEQ ID NO: 8, 9 or 11.

Applicants envision the potential use of all described isoforms andhomologs of HJV can be used in HJV fusion polypeptides of the presentinvention, with suitable modifications when necessary for activity. Inaddition, truncated polypeptides which comprise partial fragments of thefull HJV polypeptides, and which retain the ability to promote increasein serum iron and/or transferrin saturation can also be useful for thepresent invention. Fragments of HJV as the term is used herein, refersto a truncated product (from either the C-terminus or N-terminus) whichhas no other sequence modifications (e.g. internal deletions or pointmutations.) In particular, functional fragments of HJV sequences, whichretain the ability to increase iron serum and/or transferrin saturationof HJV demonstrated in the Examples herein (referred to herein as HJVfragment), are suitable for use in the present invention. Such fragmentsmay for example, be polypeptide fragments of HJV encoded by one or moreexons of the HJV gene (GeneID: 148738, RefSeq ID: NM_(—)145277, SEQ IDNO: 38 (HJV isoform b), or one or more protein regions identified in GenBank Accession Number, 148738, in various combinations. Theidentification of a partial HJV polypeptide as a functional fragment ofHJV, or functional variant of HJV can readily be determined, forexample, using the assays as described herein and in the Examples.

The fusion proteins of the present invention encompasses use of fulllength HJV or a HJV fragment and a fusion partner, e.g., an HJV.Fcfusion. The HJV fusion portion of the protein may include a soluble formof the HJV protein (e.g., lacking the GPI anchoring domain) or may beany functional fragment of HJV (e.g., a fragment capable of regulatinghepcidin or acting as BMP co-receptor). The fragment may have at least1, 2, 3, 5, 8, 10, 15, 20, 25, 50, 75, 100 amino acids deleted from theN-terminus, the C-terminus, or both, but the fragment be at least 6amino acids as discussed above. In the fusion protein shown in SEQ IDNO:1, for example, the HJV fusion protein can include amino acids 33-399of the full human HJV length protein. In other embodiments, the fusionprotein may include a portion of the 33-399 HJV sequence that is afunctional fragment of HJV (e.g., with 1, 2, 3, 5, 8, about 10, or aboutat least 15, or about at least 20, or about at least 25, or about atleast 50, or about at least 75, or about at least 100 amino acidsdeleted from the N-terminus, the C-terminus, or both). The N-terminalsignal sequence may be deleted, or alternatively replaced with anothersignal sequence (e.g., one that targets the protein to the nucleus orextracellularly). The HJV portion of the fusion protein may be at leastabout 75%, or about at least 80%, or about at least 85%, or about atleast 90%, or about at least 95%, or about at least 99%, or about 100%identical to at least a portion of the full length HJV protein (e.g.,the human protein).

In some embodiments, HJV fragments useful in a HJV fusion protein asdisclosed herein include HJV fragments comprising structural andfunctional amino acids residues. In some embodiments, a HJV fragment asdisclosed herein can be for example, but are not limited to, fragmentswhich consist essentially of amino acids between residue about 70 toabout residue 125 (fragment a), or about residue 167 to about residue256 (fragment b), or about residue 167 to about residue 327 (fragmentc), or about residue 257 to about residue 327 (fragment d), or aboutresidue 257 to about residue 400 (fragment d). Residues are based onhuman HJV sequence GenBank Accession No. Q6ZVN8 (SEQ ID NO: 61).Alternatively, other fragments can be designed as so desired taking intoaccount the structural and functional domains of human HJV protein asdemonstrated in FIG. 25.

As disclosed herein, a functional fragment as defined by the termsherein, can be generated and assessed by on one of ordinary skill in theart by simple deletion analysis. Such a fragment of SEQ ID NOS:2 to 5can be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 amino acids or morethan 10 amino acids, such as 15, 30, 50, 100 or more than 100 aminoacids deleted from the N-terminal and/or C-terminal of SEQ ID NO: 2 to5, respectively. Persons of ordinary skill in the art can easilyidentify the minimal peptide fragment of SEQ ID NO:2 to 5 useful in aHJV fusion protein by the methods as disclosed herein, by sequentiallydeleting N- and/or C-terminal amino acids from SEQ ID NO: 2 to 5 andassessing the function of the resulting peptide fragment fused to a Fcfragment. One of ordinary skill in the art can easily assess thefunction of the HJV-fragment.Fc fusion protein to increase serum ironconcentration and/or increase transferrin saturation when administeredto a mouse in vivo (as disclosed in the Examples and FIGS. 19 and 22herein) as compared to HJV-Fc corresponding to SEQ ID NO: 1, 7 or 10 asdisclosed herein. Using such an in vivo assay, if the HJV-fragment.Fcprotein has at least 30% of the biological activity of the HJV-Fccorresponding to SEQ ID NO: 1, 7 or 10 as disclosed herein, then theHJV-fragment portion of the HJV-fragment.Fc protein is considered avalid HJV-fragment and can used in fusion proteins and methods asdisclosed herein. Alternatively, one of ordinary skill in the art caneasily assess the function of the HJV-fragment.Fc fusion protein byassessing its ability to decrease basal hepcidin expression in HepGcells in vitro as compared to HJV-Fc corresponding to SEQ ID NO: 1, 7 or10 as disclosed herein, or to determine the ability of theHJV-fragment.Fc protein to decrease BMP-mediated induction of hepcidinexpression using the BRE-luciferase in vitro assay as disclosed hereinin the Examples and in FIGS. 17A-17D. Using such an in vitro assay, ifthe HJV-fragment.Fc protein has at least 30% of the biological activityof the HJV-Fc corresponding to SEQ ID NO: 1, 7 or 10 as disclosedherein, then the HJV-fragment portion of the HJV-fragment.Fc protein isconsidered a valid HJV-fragment and can used in fusion proteins andmethods as disclosed herein. In some embodiments, a fragment of SEQ IDNOs: 2 to 5 can be less than 200, or less than 150 or less than 100, orless than 50, or less than 20 amino acids of SEQ ID NOs: 2, 3, 4 or 5.In some embodiments, a fragment of SEQ ID NOs: 2, 3, 4 or 5 is less than100 peptides in length.

The present invention also features an HJV protein (to be fused with afirst fusion partner) which has been engineered (e.g., with sequencechanges such as insertions, deletions, and point mutations, or acombination thereof) to reduce proteolytic cleavage of the protein. Suchproteins may exhibit enhanced half-life in vivo and allow for eitherreduced size of dosing or frequency of administration to generate adesired therapeutic effect. Such proteins may also exhibit increasedefficacy as compared to a fusion containing the corresponding wild typeHJV sequences, such as SEQ ID NO: 1, 2, 3, 4, or 5. One example of sucha HJV polypeptide sequence is the HJV-D17A polypeptide, such as aminoacids 1-407 of SEQ ID NO:7. In one embodiment, the HJV polypeptide whichis fused to the first fusion protein are not HJV polypeptides of SEQ IDNO: 7, 10 or 30 in U.S. Pat. No. 7,319,138 (which correspond to SEQ IDNO: 62, 63 and 64 respectively herein).

As discussed above, a HJV protein or functional fragment thereof usefulin a HJV fusion protein can correspond to a human HJV isoform A (SEQ IDNO: 2) or a functional fragment or functional variant or functionalderivative thereof, where SEQ ID NO:2 is as follows:

  1 mgepgqspsp rsshgspptl stltlllllc ghahsqckil rcnaeyvsst lslrgggssg 61 alrggggggr gggvgsgglc ralrsyalct rrtartcrgd lafhsavhgi edlmiqhncs121 rqgptapppp rgpalpgags glpapdpcdy egrfsrlhgr ppgflhcasf gdphvrsfhh181 hfhtcrvqga wplldndflf vqatsspmal ganatatrkl tiifknmqec idqkvyqaev241 dnlpvafedg singgdrpgg sslsiqtanp gnhveigaay igttiiirqt agqlsfsikv301 aedvamafsa eqdlqlcvgg cppsqrlsrs ernrrgaiti dtarrlckeg lpvedayfhs361 cvfdvlisgd pnftvaaqaa ledaraflpd leklhlfpsd agvplssatl lapllsglfv421 lwlciq

In another embodiment, a HJV protein or functional fragment thereofuseful in a HJV fusion protein can correspond to a human HJV isoform B(SEQ ID NO: 3) or a functional fragment or functional variant orfunctional derivative thereof, where SEQ ID NO:3 is as follows:

  1 miqhncsrqg ptapppprgp alpgagsglp apdpcdyegr fsrlhgrppg flhcasfgdp 61 hvrsfhhhfh tcrvggawpl ldndflfvqa tsspmalgan atatrkltii fknmgecidq121 kvyqaevdnl pvafedgsin ggdrpggssl siqtanpgnh veiqaayigt tiiirqtagq181 lsfsikvaed vamafsaeqd lqlcvggcpp sqrlsrsern rrgaitidta rrlckeglpv241 edayfhscvf dvlisgdpnf tvaaqaaled araflpdlek lhlfpsdagv plssatllap301 llsglfvlwl ciq

In another embodiment, a HJV protein or functional fragment thereofuseful in a HJV fusion protein can correspond to a human HJV isoform C(SEQ ID NO: 4) or a functional fragment or functional variant orfunctional derivative thereof, where SEQ ID NO:4 is as follows:

  1 mgecidqkvy qaevdnlpva fedgsinggd rpggsslsiq tanpgnhvei qaayigttii 61 irqtagglsf sikvaedvam afsaeqdlql cvggcppsqr lsrsernrrg aitidtarrl121 ckeglpveda yfhscvfdvl isgdpnftva agaaledara flpdleklhl fpsdagvpls181 satllaplls glfvlwlciq

In another embodiment, a HJV protein or functional fragment thereofuseful in a HJV fusion protein can correspond to a mouse HJV homologue(SEQ ID NO: 5) or a functional fragment or functional variant orfunctional derivative thereof, where SEQ ID NO:5 is as follows:

  1 mqecidqkvy qaevdnlpaa fedgsinggd rpggsslsiq tanlgshvei raayigttii 61 irqtagqlsf sirvaedvar afsaeqdlql cvggcppsqr lsrsernrrg aiaidtarrl121 ckeglpveda yfqscvfdvs vsgdpnftva aqtalddary fltdlenlhl fpsdagppls181 paiclvplls alfvlwlcfs k

In one embodiment, a HJV fusion protein useful in the methods andcompositions as disclosed herein can correspond to a human HJV proteinfused to a Fc fragment, such as SEQ ID NO: 1, or alternatively where HJVis a functional fragment of HJV protein. Accordingly, in one embodiment,a HJV fusion protein useful in the methods and compositions as disclosedherein comprises SEQ ID NO: 1 or functional variants or functionalderivatives thereof, where SEQ ID NO:1 is as follows:

MSALLILALVGAAVADYKDHDGDYKDHDIDYKDDDDKLAAAHSQCKILRCNAEYVSSTLSLRGGGSSGALRGGGGGGRGGGVGSGGLCRALRSYALCTRRTARTCRGDLAFHSAVHGIEDLMIQHNCSRQGPTAPPPPRGPALPGAGSGLPAPDPCDYEGRFSRLHGRPPGFLHCASFGDPHVRSFHHHFHTCRVQGAWPLLDNDFLFVQATSSPMALGANATATRKLTIIFKNMQECIDQKVYQAEVDNLPVAFEDGSINGGDRPGGSSLSIQTANPGNHVEIQAAYIGTTIIIRQTAGQLSFSIKVAEDVAMAFSAEQDLQLCVGGCPPSQRLSRSERNRRGAITIDTARRLCKEGLPVEDAYFHSCVFDVLISGDPNFTVAAQAALEDARAFLPDLEKLHLFPSLELVPRGSGDPIEGRGGGGGDPKSCDKPHTCPLCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKATPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

In one embodiment, a HJV fusion protein useful in the methods andcompositions as disclosed herein can correspond to a human HJV proteinwhich is a non cleavable form which is fused to a Fc fragment, such asSEQ ID NO: 7, or alternatively where HJV is a functional fragment of anon-cleavable form of a HJV protein. Accordingly, in one embodiment, aHJV fusion protein useful in the methods and compositions as disclosedherein comprises SEQ ID NO: 7 or functional variants or functionalderivatives thereof, where SEQ ID NO:7 is as follows:

MSALLILALVGAAVADYKDHDGDYKDHDIDYKDDDDKLAAAHSQCKILRCNAEYVSSTLSLRGGGSSGALRGGGGGGRGGGVGSGGLCRALRSYALCTRRTARTCRGDLAFHSAVHGIEDLMIQHNCSRQGPTAPPPPRGPALPGAGSGLPAPDPCDYEGRFSRLHGRPPGFLHCASFG A PHVRSFHHHFHTCRVQGAWPLLDNDFLFVQATSSPMALGANATATRKLTIIFKNMQECIDQKVYQAEVDNLPVAFEDGSINGGDRPGGSSLSIQTANPGNHVEIQAAYIGTTIIIRQTAGQLSFSIKVAEDVAMAFSAEQDLQLCVGGCPPSQRLSRSERNRRGAITIDTARRLCKEGLPVEDAYFHSCVFDVLISGDPNFTVAAQAALEDARAFLPDLEKLHLFPSLELVPRGSGDPIEGRGGGGGDPKSCDKPHTCPLCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKATPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

In one embodiment, a HJV fusion protein useful in the methods andcompositions as disclosed herein can correspond to a human HJV fusionprotein comprising SEQ ID NO: 10 which is encoded by a polynucleotidewhich has been codon optimized, for example by polynucleotide SEQ IDNO:11 One can use the HJV protein in SEQ ID NO: 10 which has had theextracellular signal sequence and GPI anchoring domain removed.Accordingly, in one embodiment, a HJV fusion protein useful in themethods and compositions as disclosed herein comprises SEQ ID NO: 10 orfunctional variants or functional derivatives thereof, where SEQ IDNO:10 is as follows:

MSALLILALVGAAVAHSQCKILRCNAEYVSSTLSLRGGGSSGALRGGGGGGRGGGVGSGGLCRALRSYALCTRRTARTCRGDLAFHSAVHGIEDLMIQHNCSRQGPTAPPPPRGPALPGAGSGLPAPDPCDYEGRFSRLHGRPPGFLHCASFGDPHVRSFHHHFHTCRVQGAWPLLDNDFLFVQATSSPMALGANATATRKLTIIFKNMQECIDQKVYQAEVDNLPVAFEDGSINGGDRPGGSSLSIQTANPGNHVEIQAAYIGTTIIIRQTAGQLSFSIKVAEDVAMAFSAEQDLQLCVGGCPPSQRLSRSERNRRGAITIDTARRLCKEGLPVEDAYFHSCVFDVLISGDPNFTVAAQAALEDARAFLPDLEKLHLFPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

It will be appreciated that the HJV polypeptides useful for the HJVfusion proteins as disclosed herein often contain amino acids other thanthe 20 amino acids commonly referred to as the 20 naturally occurringamino acids, and many amino acids, including the terminal amino acids,can be modified either by natural processes such as glycosylation andother post-translational modifications, or by chemical modificationtechniques which are well known in the art. Even the commonmodifications that occur naturally in polypeptides are too numerous tolist exhaustively here, but they are well described in basic texts andin more detailed monographs, as well as in a voluminous researchliterature, and they are well known to those of skill in the art. Amongthe known modifications which can be present in polypeptides of thepresent invention are, to name an illustrative few, acetylation,acylation, ADP-ribosylation, amidation, covalent attachment of flavin,covalent attachment of a heme moiety, covalent attachment of apolynucleotide or polynucleotide derivative, covalent attachment of alipid or lipid derivative, covalent attachment of phosphotidylinositol,cross-linking, cyclization, disulfide bond formation, demethylation,formation of covalent cross-links, formation of cysteine, formation ofpyroglutamate, formylation, gamma-carboxylation, glycation,glycosylation, hydroxylation, iodination, methylation, myristoylation,oxidation, proteolytic processing, phosphorylation, prenylation,racemization, selenoylation, sulfation, transfer-RNA mediated additionof amino acids to proteins such as arginylation, and ubiquitination.

Such modifications are well known to those of skill and have beendescribed in great detail in the scientific literature. Severalparticularly common modifications, glycosylation, lipid attachment,sulfation, gamma-carboxylation of glutamic acid residues, hydroxylationand ADP-ribosylation, for instance, are described in most basic texts,such as, for instance, 1. E. Creighton, Proteins-Structure and MolecularProperties, 2nd Ed., W.H. Freeman and Company, New York, 1993. Manydetailed reviews are available on this subject, such as, for example,those provided by Wold, F., in Posttranslational Covalent Modificationof Proteins, B. C. Johnson, Ed., Academic Press, New York, pp 1-12,1983; Sifter et al., Meth. Enzymol. 182: 626-646, 1990 and Rattan etal., Protein Synthesis: Posttranslational Modifications and Aging, Ann.N.Y. Acad. Sci. 663: 48-62, 1992.

It will also be appreciated, as is well known and as noted above, thatpeptides and polypeptides are not always entirely linear. For instance,polypeptides can be branched as a result of ubiquitination, and they canbe circular, with or without branching, generally as a result ofposttranslational events, including natural processing events and eventsbrought about by human manipulation which do not occur naturally.Circular, branched and branched circular polypeptides can be synthesizedby non translational natural processes and by entirely syntheticmethods.

Modifications can occur anywhere in a polypeptide, including the peptidebackbone, the amino acid side-chains and the amino or carboxyl termini.In fact, blockage of the amino or carboxyl group in a polypeptide, orboth, by a covalent modification, is common in naturally occurring and;synthetic polypeptides and such modifications can be present inpolypeptides of the present invention, as well. For instance, the aminoterminal residue of polypeptides made in E. coli, prior to proteolyticprocessing, almost invariably will be N-formylmethionine.

The modifications that occur in a polypeptide often will be a functionof how it is made. For polypeptides made by expressing a cloned gene ina host, for instance, the nature and extent of the modifications inlarge part will be determined by the host cell posttranslationalmodification capacity and the modification signals present in thepolypeptide amino acid sequence. For instance, as is well known,glycosylation often does not occur in bacterial hosts such as E. coli.Accordingly, when glycosylation is desired, a polypeptide should beexpressed in a glycosylation host, generally a eukaryotic cell. Insectcells often carry out the same posttranslational glycosylation asmammalian cells and, for this reason, insect cell expression systemshave been developed to efficiently express mammalian proteins havingnative patterns of glycosylation, inter alia. Similar considerationsapply to other modifications.

It will be appreciated that the same type of modification can be presentto the same or varying degree at several sites in a given polypeptide.Also, a given peptide or polypeptide can contain many types ofmodifications.

In some embodiments, N-methyl and hydroxy-amino acids can be substitutedfor conventional amino acids in solid phase peptide synthesis. However,production of polymers with reduced peptide bonds requires synthesis ofthe dimmer of amino acids containing the reduced peptide bond. Suchdimers are incorporated into polymers using standard solid phasesynthesis procedures. Other synthesis procedures are well known in theart.

III. HJV Fusion Proteins and Protein Conjugation

In some embodiments, a HJV polypeptide (i.e. SEQ ID NOs: 2 to 5 orfragments, derivatives or variants thereof) are conjugated to a firstfusion partner (i.e. IgG1 Fc). The conjugation can be a non-covalent orcovalent interaction, for example, by means of chemical crosslinkage orconjugation.

As disclosed herein, the inventors have developed HJV-D172A.Fc (SEQ IDNO:7), an HJV.Fc fusion which exhibits reduced proteolytic cleavage ascompared to the fusion protein including the corresponding wild typesequence (SEQ ID NO:1). The inventors have also developed a HJV.Fc (SEQID NO:10) which has been codon-optimized for expression in mammaliancells, an HJV.Fc fusion protein which exhibits the nucleotide bases morecommon to mammalian cell than bacterial cells as compared to thecorresponding wildtype sequence (SEQ ID NO:1).

In some embodiments, the polynucleotides encoding any of the fusionproteins (e.g., SEQ ID NOS: 8, 9 and 11) may be produced using anymolecular biological techniques known in the art (e.g., those describedherein).

In one embodiment, a HJV fusion protein useful in the methods andcompositions as disclosed herein can correspond to a human HJV fusionprotein which is encoded by a polynucleotide which has been codonoptimized such as the polynucleotide sequence of SEQ ID NO: 11. Thepolynucleotide of SEQ ID NO:11 is codon-optimized for protein expressionin mammalian cells and encodes for a HJV fusion protein where the HJVprotein has had the extracellular signal sequence and GPI anchoringdomain removed. Accordingly, in one embodiment, a polynucleotide usefulfor encoding and producing a HJV fusion protein for use in the methodsand compositions as disclosed herein comprises SEQ ID NO: 11 oranalogues, variants or derivatives thereof, where SEQ ID NO:11 is asfollows:

GGATCCAAGCTTgccgccATGAGCGCCCTGCTTATTCTGGCCCTGGTTGGAGCAGCCGTGGCTCATAGCCAGTGCAAGATCCTGCGATGCAATGCCGAGTACGTGTCTTCCACCCTCAGTCTCAGAGGCGGGGGGAGTTCCGGCGCACTGCGCGGGGGAGGTGGAGGTGGCCGCGGAGGCGGAGTGGGATCTGGGGGACTGTGCCGAGCTTTGCGGAGTTACGCTCTGTGCACAAGACGCACCGCCAGGACCTGCAGGGGAGACCTGGCATTCCACAGCGCAGTGCACGGCATTGAAGACTTGATGATTCAGCATAATTGTAGTAGACAAGGCCCTACCGCTCCCCCCCCTCCCAGGGGCCCCGCTTTGCCTGGGGCAGGTTCCGGACTGCCCGCCCCAGATCCTTGTGACTACGAGGGGCGGTTCAGCCGACTCCATGGAAGGCCCCCAGGCTTCCTGCACTGCGCAAGTTTTGGCGATCCACACGTCAGGTCATTTCACCACCACTTTCATACCTGTCGTGTCCAGGGCGCATGGCCTCTGCTGGACAACGACTTCCTCTTCGTCCAAGCAACAAGTTCACCTATGGCTCTGGGGGCAAATGCTACTGCCACCCGAAAACTTACCATTATCTTTAAGAATATGCAAGAATGTATCGATCAGAAGGTCTACCAGGCCGAAGTTGACAACCTGCCCGTGGCTTTCGAGGATGGTTCAATCAACGGAGGGGACCGGCCTGGAGGCTCCAGTCTGAGCATCCAGACCGCCAATCCTGGAAATCACGTGGAGATCCAGGCTGCCTACATCGGCACAACAATCATAATTAGGCAGACCGCTGGCCAGCTGAGCTTCTCCATCAAGGTCGCCGAAGACGTGGCCATGGCTTTCTCTGCCGAACAGGACCTCCAGCTTTGCGTGGGTGGTTGTCCACCCTCCCAGCGCCTTTCTCGATCCGAACGCAATAGGCGAGGCGCAATCACTATCGACACTGCTCGCAGATTGTGCAAAGAGGGCCTGCCTGTGGAGGATGCATACTTCCATTCTTGTGTGTTCGACGTCCTGATAAGCGGAGACCCAAATTTCACAGTGGCTGCTCAGGCCGCACTGGAGGATGCCAGGGCCTTTTTGCCCGATCTGGAAAAGTTGCATCTGTTCCCAAAATCCTGTGACAAGACTCATACCTGTCCACCGTGTCCCGCCCCCGAACTCTTGGGCGGGCCTTCTGTGTTCCTCTTCCCACCCAAACCAAAAGACACACTGATGATCTCCAGGACCCCTGAAGTGACTTGCGTCGTGGTTGACGTGTCTCATGAAGACCCCGAGGTGAAGTTCAACTGGTACGTCGATGGAGTGGAGGTTCATAACGCCAAGACAAAACCAAGGGAGGAACAATACAACTCTACATACAGGGTGGTCAGTGTGCTGACTGTGCTGCACCAGGACTGGCTCAACGGCAAAGAGTACAAATGCAAGGTGTCTAACAAGGCACTTCCTGCTCCAATTGAAAAAACCATCTCCAAGGCTAAGGGGCAGCCAAGGGAACCACAGGTGTATACTCTTCCTCCTTCTCGCGACGAACTGACTAAAAATCAGGTGTCATTGACCTGTCTGGTGAAGGGCTTTTACCCCTCCGATATAGCTGTGGAGTGGGAGAGCAACGGGCAGCCCGAGAACAATTATAAAACCACACCACCTGTCCTCGACAGTGATGGATCATTTTTCCTCTACAGTAAGCTGACCGTGGATAAATCTAGGTGGCAGCAGGGGAACGTGTTTTCTTGCTCCGTGATGCACGAGGCCCTTCACAACCATTACACACAGAAGAGCCTGAGCCTGTCCCCAGGAAAG

GAATTCGCGGCCGC(BamHI/HindIII linker sites are in italics; Kozak sequencein lower case; Start codon in bold; EcoRI/NotI linker sitesare in italics; Stop Codon in bold italics).

In another embodiment, a HJV fusion protein useful in the methods andcompositions as disclosed herein can correspond to a human HJV fusionprotein which has been modified to more proteolytically stable and is anon-cleavable variant of HJV, and can be encoded by the polynucleotidesequence of SEQ ID NO: 9. The polynucleotide of SEQ ID NO:9 has anucleotide differences to result in the encoded HJV protein to have aD172A variation which is non-cleavable. Accordingly, in one embodiment,a polynucleotide useful for encoding and producing a HJV fusion proteinfor use in the methods and compositions as disclosed herein comprisesSEQ ID NO: 9 or analogues, variants or derivatives thereof, where SEQ IDNO:9 is as follows:

ATG  TCT GCA CTT ctg atc cta gct ctt gtt gga gct gca gtt gct gactac aaa gac cat gac ggt gat tat aaa gat cat gac atc gat tac aaggat gac gat gac aag ctt gcg gcc gcT CAT TCT CAA TGC AAG ATC CTCCGC TGC AAT GCT GAG TAC GTA TCG TCC ACT CTG AGC CTT AGA GGT GGGGGT TCA TCA GGA GCA CTT CGA GGA GGA GGA GGA GGA GGC CGG GGT GGAGGG GTG GGC TCT GGC GGC CTC TGT CGA GCC CTC CGC TCC TAT GCG CTCTGC ACT CGG CGC ACC GCC CGC ACC TGC CGC GGG GAC CTC GCC TTC CATTCG GCG GTA CAT GGC ATC GAA GAC CTG ATG ATC CAG CAC AAC TGC TCCCGC CAG GGC CCT ACA GCC CCT CCC CCG CCC CGG GGC CCC GCC CTT CCAGGC GCG GGC TCC GGC CTC CCT GCC CCG GAC CCT TGT GAC TAT GAA GGCCGG TTT TCC CGG CTG CAT GGT CGT CCC CCG GGG TTC TTG CAT TGC GCTTCC TTC GGG G C C CCC CAT GTG CGC AGC TTC CAC CAT CAC TTT CAC ACATGC CGT GTC CAA GGA GCT TGG CCT CTA CTG GAT AAT GAC TTC CTC TTTGTC CAA GCC ACC AGC TCC CCC ATG GCG TTG GGG GCC AAC GCT ACC GCCACC CGG AAG CTC ACC ATC ATA TTT AAG AAC ATG CAG GAA TGC ATT GATCAG AAG GTG TAT CAG GCT GAG GTG GAT AAT CTT CCT GTA GCC TTT GAAGAT GGT TCT ATC AAT GGA GGT GAC CGA CCT GGG GGA TCC AGT TTG TCGATT CAA ACT GCT AAC CCT GGG AAC CAT GTG GAG ATC CAA GCT GCC TACATT GGC ACA ACT ATA ATC ATT CGG CAG ACA GCT GGG CAG CTC TCC TTCTCC ATC AAG GTA GCA GAG GAT GTG GCC ATG GCC TTC TCA GCT GAA CAGGAC CTG CAG CTC TGT GTT GGG GGG TGC CCT CCA AGT CAG CGA CTC TCTCGA TCA GAG CGC AAT CGT CGG GGA GCT ATA ACC ATT GAT ACT GCC AGACGG CTG TGC AAG GAA GGG CTT CCA GTG GAA GAT GCT TAC TTC CAT TCCTGT GTC TTT GAT GTT TTA ATT TCT GGT GAT CCC AAC TTT ACC GTG GCAGCT CAG GCA GCA CTG GAG GAT GCC CGA GCC TTC CTG CCA GAC TTA GAGAAG CTG CAT CTC TTC CCC TCA ctc gag ctg gtt ccg cgt ggt tcg GgGGAT CCC ATC GAA GGT CGT GGT GGT GGT GGT GGT GAT CCC AAA TCT TGTGAC AAA CCT CAC ACA TGC CCA CTG TGC CCA GCA CCT GAA CTC CTG GGGGGA CCG TCA GTC TTC CTC TTC CCC CCA AAA CCC AAG GAC ACC CTC ATGATC TCC CGG ACC CCT GAG GTC ACA TGC GTG GTG GTG GAC GTG AGC CACGAA GAC CCT GAG GTC AAG TTC AAC TGG TAC GTG GAC GGC GTG GAG GTGCAT AAT GCC AAG ACA AAG CCG CGG GAG GAG CAG TAC AAC AGC ACG TACCGT GTG GTC AGC GTC CTC ACC GTC CTG CAC CAG GAC TGG CTG AAT GGCAAG GAG TAC AAG TGC AAG GTC TCC AAC AAA GCC CTC CCA GCC CCC ATCGAG AAA ACC ATC TCC AAA GCC AAA GGG CAG CCC CGA GAA CCA CAG GTGTAC ACC CTG CCC CCA TCC CGG GAT GAG CTG ACC AAG AAC CAG GTC AGCCTG ACC TGC CTA GTC AAA GGC TTC TAT CCC AGC GAC ATC GCC GTG GAGTGG GAG AGC AAT GGG CAG CCG GAG AAC AAC TAC AAG GCC ACG CCT CCCGTG CTG GAC TCC GAC GGC TCC TTC TTC CTC TAC AGC AAG CTC ACC GTGGAC AAG AGC AGG TGG CAG CAG GGG AAC GTC TTC TCA TGC TCC GTG ATGCAT GAG GCT CTG CAC AAC CAC TAC ACG CAG AAG AGC CTC TCC CTG TCTCCG GGT AAA 

(Kozak sequence are identified as being in lower case; Startcodon in bold; Stop Codon in bold italics).

In another embodiment, a HJV fusion protein useful in the methods andcompositions as disclosed herein can correspond to a human HJV fusionprotein encoded by the polynucleotide sequence of SEQ ID NO: 8.Accordingly, in one embodiment, a polynucleotide useful for encoding andproducing a HJV fusion protein for use in the methods and compositionsas disclosed herein comprises SEQ ID NO: 8 or analogues, variants orderivatives thereof, where SEQ ID NO: 8 is as follows:

ATG  TCT GCA CTT ctg atc cta gct ctt gtt gga gct gca gtt gctgac tac aaa gac cat gac ggt gat tat aaa gat cat gac atc gat tacaag gat gac gat gac aag ctt gcg gcc gcT CAT TCT CAA TGC AAG ATCCTC CGC TGC AAT GCT GAG TAC GTA TCG TCC ACT CTG AGC CTT AGA GGTGGG GGT TCA TCA GGA GCA CTT CGA GGA GGA GGA GGA GGA GGC CGG GGTGGA GGG GTG GGC TCT GGC GGC CTC TGT CGA GCC CTC CGC TCC TAT GCGCTC TGC ACT CGG CGC ACC GCC CGC ACC TGC CGC GGG GAC CTC GCC TTCCAT TCG GCG GTA CAT GGC ATC GAA GAC CTG ATG ATC CAG CAC AAC TGCTCC CGC CAG GGC CCT ACA GCC CCT CCC CCG CCC CGG GGC CCC GCC CTTCCA GGC GCG GGC TCC GGC CTC CCT GCC CCG GAC CCT TGT GAC TAT GAAGGC CGG TTT TCC CGG CTG CAT GGT CGT CCC CCG GGG TTC TTG CAT TGCGCT TCC TTC GGG GAC CCC CAT GTG CGC AGC TTC CAC CAT CAC TTT CACACA TGC CGT GTC CAA GGA GCT TGG CCT CTA CTG GAT AAT GAC TTC CTCTTT GTC CAA GCC ACC AGC TCC CCC ATG GCG TTG GGG GCC AAC GCT ACCGCC ACC CGG AAG CTC ACC ATC ATA TTT AAG AAC ATG CAG GAA TGC ATTGAT CAG AAG GTG TAT CAG GCT GAG GTG GAT AAT CTT CCT GTA GCC TTTGAA GAT GGT TCT ATC AAT GGA GGT GAC CGA CCT GGG GGA TCC AGT TTGTCG ATT CAA ACT GCT AAC CCT GGG AAC CAT GTG GAG ATC CAA GCT GCCTAC ATT GGC ACA ACT ATA ATC ATT CGG CAG ACA GCT GGG CAG CTC TCCTTC TCC ATC AAG GTA GCA GAG GAT GTG GCC ATG GCC TTC TCA GCT GAACAG GAC CTG CAG CTC TGT GTT GGG GGG TGC CCT CCA AGT CAG CGA CTCTCT CGA TCA GAG CGC AAT CGT CGG GGA GCT ATA ACC ATT GAT ACT GCCAGA CGG CTG TGC AAG GAA GGG CTT CCA GTG GAA GAT GCT TAC TTC CATTCC TGT GTC TTT GAT GTT TTA ATT TCT GGT GAT CCC AAC TTT ACC GTGGCA GCT CAG GCA GCA CTG GAG GAT GCC CGA GCC TTC CTG CCA GAC TTAGAG AAG CTG CAT CTC TTC CCC TCA ctc gag ctg gtt ccg cgt ggt tcgGgG GAT CCC ATC GAA GGT CGT GGT GGT GGT GGT GGT GAT CCC AAA TCTTGT GAC AAA CCT CAC ACA TGC CCA CTG TGC CCA GCA CCT GAA CTC CTGGGG GGA CCG TCA GTC TTC CTC TTC CCC CCA AAA CCC AAG GAC ACC CTCATG ATC TCC CGG ACC CCT GAG GTC ACA TGC GTG GTG GTG GAC GTG AGCCAC GAA GAC CCT GAG GTC AAG TTC AAC TGG TAC GTG GAC GGC GTG GAGGTG CAT AAT GCC AAG ACA AAG CCG CGG GAG GAG CAG TAC AAC AGC ACGTAC CGT GTG GTC AGC GTC CTC ACC GTC CTG CAC CAG GAC TGG CTG AATGGC AAG GAG TAC AAG TGC AAG GTC TCC AAC AAA GCC CTC CCA GCC CCCATC GAG AAA ACC ATC TCC AAA GCC AAA GGG CAG CCC CGA GAA CCA CAGGTG TAC ACC CTG CCC CCA TCC CGG GAT GAG CTG ACC AAG AAC CAG GTCAGC CTG ACC TGC CTA GTC AAA GGC TTC TAT CCC AGC GAC ATC GCC GTGGAG TGG GAG AGC AAT GGG CAG CCG GAG AAC AAC TAC AAG GCC ACG CCTCCC GTG CTG GAC TCC GAC GGC TCC TTC TTC CTC TAC AGC AAG CTC ACCGTG GAC AAG AGC AGG TGG CAG CAG GGG AAC GTC TTC TCA TGC TCC GTGATG CAT GAG GCT CTG CAC AAC CAC TAC ACG CAG AAG AGC CTC TCC CTGTCT CCG GGT AAA 

(Kozak sequence are identified as being in lower case; Startcodon in bold; Stop Codon in bold italics).

The HJV protein may be fused to one or more fusion partners. In certainembodiments, one of the fusion partners is the Fc protein (e.g., mouseFc or human Fc). The fusion protein may further include a second fusionpartner such as a purification or detection tag, for example, proteinsthat may be detected directly or indirectly such as green fluorescentprotein, hemagglutinin, or alkaline phosphatase), DNA binding domains(for example, GAL4 or LexA), gene activation domains (for example, GAL4or VP16), purification tags, or secretion signal peptides (e.g.,preprotyrypsin signal sequence). In other embodiments the fusion partnermay be a tag, such as c-myc, poly histidine, or FLAG. Each fusionpartner may contain one or more domains, e.g., a preprotrypsin signalsequence and FLAG tag.

In one embodiment, a HJV fusion protein useful in the methods andcompositions as disclosed herein can comprise a human Fc protein or afunctional fragment thereof. Accordingly, in one embodiment, a HJVfusion protein useful in the methods and compositions as disclosedherein can comprises a human Fc molecule as the first fusion partner,where the Fc fragment can be SEQ ID NO: 6 or functional variants orfunctional derivatives thereof, where SEQ ID NO: 6 is as follows:

LELVPRGSGDPIEGRGGGGGDPKSCDKPHTCPLCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKATPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

Variations and modifications to the HJV protein and vectors can be usedto increase or decrease HJV fusion protein expression, and to providemeans for targeting. For example, the HJV fusion protein can be linkedwith a molecular targeting molecule for muscle cells, to make these HJVfusion proteins tissue specific.

In one embodiment, the HJV fusion proteins is fused to a second fusionpartner, such as a carrier molecule to enhance its bioavailability. Suchcarriers are known in the art and include poly (alkyl) glycol such aspoly ethylene glycol (PEG). Fusion to serum albumin can also increasethe serum half-life of therapeutic polypeptides.

The HJV fusion polypeptide can also be fused to a second fusion partner,for example, to a polypeptide that targets the product to a desiredlocation, or, for example, a tag that facilitates its purification, ifso desired. Tags and fusion partners can be designed to be cleavable, ifso desired. Another modification specifically contemplated isattachment, e.g., covalent attachment, to a polymer. In one aspect,polymers such as polyethylene glycol (PEG) or methoxypolyethylene glycol(mPEG) can increase the in vivo half-life of proteins to which they areconjugated. Methods of PEGylation of polypeptide agents are well knownto those skilled in the art, as are considerations of, for example, howlarge a PEG polymer to use.

As used herein, the term “conjugate” or “conjugation” refers to theattachment of two or more entities to form one entity. For example, themethods of the present invention provide conjugation of a HJVpolypeptide (i.e. SEQ ID NO: 2-5 or fragments, derivatives or variantsthereof) joined with another entity, for example a moiety such as afirst fusion partner that makes the HJV stable, such as Ig carrierparticle, for example IgG1 Fc. The attachment can be by means oflinkers, chemical modification, peptide linkers, chemical linkers,covalent or non-covalent bonds, or protein fusion or by any means knownto one skilled in the art. The joining can be permanent or reversible.In some embodiments, several linkers can be included in order to takeadvantage of desired properties of each linker and each protein in theconjugate. Flexible linkers and linkers that increase the solubility ofthe conjugates are contemplated for use alone or with other linkers asdisclosed herein. Peptide linkers can be linked by expressing DNAencoding the linker to one or more proteins in the conjugate. Linkerscan be acid cleavable, photocleavable and heat sensitive linkers.Methods for conjugation are well known by persons skilled in the art andare encompassed for use in the present invention.

According to the present invention, the HJV polypeptide (i.e. SEQ ID NO:2-5 or fragments, derivatives or variants thereof), can be linked to thefirst fusion partner via any suitable means, as known in the art, seefor example U.S. Pat. Nos. 4,625,014, 5,057,301 and 5,514,363, which areincorporated herein in their entirety by reference. For example, the HJVpolypeptide can be covalently conjugated to the IgG1 Fc, either directlyor through one or more linkers. In one embodiment, a HJV polypeptide asdisclosed herein is conjugated directly to the first fusion partner(e.g. Fc), and in an alternative embodiment, a HJV polypeptide asdisclosed herein can be conjugated to a first fusion partner (such asIgG1 Fc) via a linker, e.g. a transport enhancing linker.

A large variety of methods for conjugation of a HJV polypeptide asdisclosed herein with a first fusion partner (e.g. Fc) are known in theart. Such methods are e.g. described by Hermanson (1996, BioconjugateTechniques, Academic Press), in U.S. Pat. No. 6,180,084 and U.S. Pat.No. 6,264,914 which are incorporated herein in their entirety byreference and include e.g. methods used to link haptens to carriersproteins as routinely used in applied immunology (see Harlow and Lane,1988, “Antibodies: A laboratory manual”, Cold Spring Harbor LaboratoryPress, Cold Spring Harbor, N.Y.). It is recognized that, in some cases,a HJV polypeptide can lose efficacy or functionality upon conjugationdepending, e.g., on the conjugation procedure or the chemical grouputilized therein. However, given the large variety of methods forconjugation the skilled person is able to find a conjugation method thatdoes not or least affects the efficacy or functionality of the entities,such as the HJV polypeptide to be conjugated.

Suitable methods for conjugation of a HJV polypeptide as disclosedherein with a first fusion partner (e.g. Fc) include e.g. carbodimideconjugation (Bauminger and Wilchek, 1980, Meth. Enzymol. 70: 151-159).Alternatively, a moiety can be coupled to a targeting agent as describedby Nagy et al., Proc. Natl. Acad. Sci. USA 93:7269-7273 (1996), and Nagyet al., Proc. Natl. Acad. Sci. USA 95:1794-1799 (1998), each of whichare incorporated herein by reference. Another method for conjugating onecan use is, for example sodium periodate oxidation followed by reductivealkylation of appropriate reactants and glutaraldehyde crosslinking.

One can use a variety of different linkers to conjugate a HJVpolypeptide as disclosed herein with a first fusion partner (e.g. Fc),for example but not limited to aminocaproic horse radish peroxidase(HRP) or a heterobiofunctional cross-linker, e.g. carbonyl reactive andsulfhydryl-reactive cross-linker. Heterobiofunctional cross linkingreagents usually contain two reactive groups that can be coupled to twodifferent function targets on proteins and other macromolecules in a twoor three-step process, which can limit the degree of polymerizationoften associated with using homobiofunctional cross-linkers. Suchmulti-step protocols can offer a great control of conjugate size and themolar ratio of components.

The term “linker” refers to any means to join two or more entities, forexample a HJV polypeptide as disclosed herein with a first fusionpartner (e.g. Fc). A linker can be a covalent linker or a non-covalentlinker. Examples of covalent linkers include covalent bonds or a linkermoiety covalently attached to one or more of the proteins to be linked.The linker can also be a non-covalent bond, e.g. an organometallic bondthrough a metal center such as platinum atom. For covalent linkages,various functionalities can be used, such as amide groups, includingcarbonic acid derivatives, ethers, esters, including organic andinorganic esters, amino, urethane, urea and the like. To provide forlinking, the effector molecule and/or the probe can be modified byoxidation, hydroxylation, substitution, reduction etc. to provide a sitefor coupling. It will be appreciated that modification which do notsignificantly decrease the function of the HJV polypeptide as disclosedherein or the first fusion partner (e.g. Fc) are preferred.

IV. Polypeptide Expression

In general, HJV fusion proteins may be produced by transformation of asuitable host cell with all or part of a polypeptide-encodingpolynucleotide molecule or fragment thereof in a suitable expressionvehicle.

Those skilled in the field of molecular biology will understand that anyof a wide variety of expression systems may be used to provide therecombinant polypeptide. The precise host cell used is not critical tothe invention. A polypeptide of the invention may be produced in aprokaryotic host (e.g., E. coli) or in a eukaryotic host (e.g.,Saccharomyces cerevisiae, insect cells, e.g., Sf21 cells, or mammaliancells, e.g., NIH 3T3, HeLa, or preferably COS or CHO cells). Such cellsare available from a wide range of sources (e.g., the American TypeCulture Collection, Rockland, Md.; also, see, e.g., Ausubel et al.,supra). The method of transformation or transfection and the choice ofexpression vehicle will depend on the host system selected.Transformation and transfection methods are described, e.g., in Ausubelet al. (supra); expression vehicles may be chosen from those provided,e.g., in Cloning Vectors: A Laboratory Manual (Pouwels, P. H. et al.,1985, Supp. 1987).

One particular bacterial expression system for polypeptide production isthe E. coli pET expression system (Novagen, Inc., Madison, Wis.).According to this expression system, DNA encoding a polypeptide isinserted into a pET vector in an orientation designed to allowexpression. Since the gene encoding such a polypeptide is under thecontrol of the T7 regulatory signals, expression of the polypeptide isachieved by inducing the expression of T7 RNA polymerase in the hostcell. This is typically achieved using host strains which express T7 RNApolymerase in response to IPTG induction. Once produced, recombinantpolypeptide is then isolated according to standard methods known in theart, for example, those described herein.

Another bacterial expression system for polypeptide production is thepGEX expression system (Pharmacia). This system employs a GST genefusion system which is designed for high-level expression of genes orgene fragments as fusion proteins with rapid purification and recoveryof functional gene products. The polypeptide of interest is fused to thecarboxyl terminus of the glutathione S-transferase protein fromSchistosoma japonicum and is readily purified from bacterial lysates byaffinity chromatography using Glutathione Sepharose 4B. Fusion proteinscan be recovered under mild conditions by elution with glutathione.Cleavage of the glutathione S-transferase domain from the fusion proteinis facilitated by the presence of recognition sites for site-specificproteases upstream of this domain. For example, polypeptides expressedin pGEX-2T plasmids may be cleaved with thrombin; those expressed inpGEX-3X may be cleaved with factor Xa.

Commercial scale production of proteins using mammalian cells, such asCHO cells, is desirable in certain embodiments (see, e.g., Wurm, Nat.Biotechnol. 22:1393-1398, 2004). Techniques for optimizing expression inmammalian cells, such as introducing an intron into the cDNA sequence(e.g., between the promoter and the coding sequence), linearization ofthe plasmid DNA prior to transfection, and use of flank sequences todirect the integration of the construct into a region of the genome thatwill provide higher expression may be employed. In addition, the choiceof media can be critical as well.

Wurm (supra) describes formats used for commercial scale mammalian cellculture as follows.

Adherent Cell Culture.

CHO cells are seeded into roller bottles that are filled to 10-30% ofcapacity with medium and slowly rotated, allowing cells to adhere. Therotation assures a regular wetting of the cells and oxygen is suppliedby the ample ‘head space’ in the bottle. After a period of growth andmaintenance of the culture at confluency for a few days, the product isharvested from the decanted supernatant. The process can be scaled-upeasily because the number of roller bottles handled in paralleldetermines scale. Product concentrations in the 50-200 mg/l range arepossible, providing protein in the kilogram range annually.

Adherent cells have also been cultivated on polymer spheres termedmicrocarriers that are maintained in suspension in stirred-tankbioreactors. They allow for easy scale-up in bioreactors. CHO cells onmicrocarriers are being used for the production of follicle stimulatinghormone and of virus-vaccines.

Suspension Culture.

CHO cells now dominate the domain of mass production of recombinantprotein products because of their capacity for single-cell suspensiongrowth. Other cell lines grown well in suspension are mousemyeloma-derived N50 cells, BHK, HEK-293 and human retina-derived PER-C6cells. With the exception of blood-derived cells (NS0), most establishedcell lines maintain their anchorage-dependent character unless specialefforts are undertaken to adapt them to suspension growth. Commerciallyavailable media formulations allow for suspension growth. It mayrequires screening several media formulations that support thesuspension growth.

In a ‘simple’ batch or extended batch production process, the scale-upto very large volumes can occur by the dilution of the content of abioreactor into 5-20 volumes of fresh medium held prewarmed in a largerreactor. The entire process from the thawing of banked cells to theproduction vessel consists of three separate phases-seed train, inoculumtrain and production phase. The seed train is usually performed at asmall scale to provide fresh cells for scale-up during the period chosenfor the production. The inoculum train starts with a small volume ofcell suspension from the seed train and its volume is expanded so that asufficient cell number will be generated for the final production phase.Process conditions optimized for a given cell line can rarely beconsidered generic, because mammalian cell lines have a highlyindividual character highlighted by different glucose consumption rates,lactate production rates and sensitivity towards stress signals.

Although the timing of the termination (that is, harvest) of a cultureis driven mainly by plant capacity and productivity kinetics, anotherimportant factor is the quality of the derived product. The continuouslychanging composition of the culture medium during the production phasecan affect the quality of earlier synthesized product throughdegradative activities mediated by cell-released enzymes. Also, adiminishing supply of nutrients as energy providers or as buildingblocks for the synthesized product can change its molecular composition.Reproducible processes will, however, produce populations of proteinmolecules within a definable range of molecular variation.

Most high-yielding processes today are extended batch cultures wherebymedium components are added in small batches or semi-continuously. Thedevelopment of these extended batch processes requires a goodunderstanding of the cell line and the product, and is usually onlyapplied to processes that supply material for phase 3 clinical trialsand for the market.

An entirely different philosophy for manufacturing is represented bycontinuously perfused production processes. Perfused cultures canachieve even higher cell densities than batch or extended batch culturesand can be maintained for many weeks and months, with product harvestsoccurring repeatedly throughout that period. Several reactor volumes offresh medium can be fed into the culture per day, while the same volumeis being withdrawn from the reactor. The antihemophilic factor VIII(Kogenate, Bayer, Berkeley, Calif., USA), of which the market requiresabout 150 g per year, is reliably being manufactured using perfusiontechnology with suspension-cultivated BHK cells. Factor VIII maybe thelargest protein (2,332 amino acids) ever produced in bioreactors. It isharvested continuously from ongoing perfusion cultures. This verysophisticated, highly controlled process runs for up to 6 months andassures that the fragile protein is of reproducibly high quality.

Once the recombinant polypeptide of the invention is expressed, it isisolated, e.g., using affinity chromatography. In one example, anantibody (e.g., produced as described herein) raised against apolypeptide of the invention may be attached to a column and used toisolate the recombinant polypeptide. Lysis and fractionation ofpolypeptide-harboring cells prior to affinity chromatography may beperformed by standard methods (see, e.g., Ausubel et al., supra).

Once isolated, the recombinant polypeptide can, if desired, be furtherpurified, e.g., by high performance liquid chromatography (see, e.g.,Fisher, Laboratory Techniques In Biochemistry And Molecular Biology,eds., Work and Burdon, Elsevier, 1980).

Polypeptides of the invention, particularly short peptide fragments, canalso be produced by chemical synthesis (e.g., by the methods describedin Solid Phase Peptide Synthesis, 2nd ed., 1984 The Pierce Chemical Co.,Rockford, Ill.).

These general techniques of polypeptide expression and purification canalso be used to produce and isolate useful peptide fragments or analogs(described herein). In certain embodiments, a combination of techniquesmay be used to generate the fusion protein. For example, HJV and itsfirst fusion partner may be produced recombinantly and purified, or maybe purified from a natural source, and then chemically coupled togetherto form the fusion protein.

V. Treatment Methods of the Invention

One aspect of the present invention relates to the use of an HJV fusionprotein or polynucleotide encoding an HJV fusion protein to beadministered to a mammal (e.g., a human) for the treatment of a subjectsuffering from any HJV, hepcidin, or BMP-related disorder (e.g., anemiaof inflammatory states).

Examples of these disorders include, but are not limited to,iron-related disorders such as hemochromatosis, ferroportin mutationhemochromatosis, transferrin receptor 2 mutation hemochromatosis,juvenile hemochromatosis, neonatal hemochromatosis, hepcidin deficiency,transfusional iron overload, thalassemia, thalassemia intermedia, alphathalassemia, sideroblastic anemia, porphyria, porphyria cutanea tarda,African iron overload, hyperferritinemia, ceruloplasmin deficiency,atransferrinemia, congenital dyserythropoietic anemia, anemia of chronicdisease, anemia, hypochromic microcytic anemia, iron-deficiency anemia,conditions with hepcidin excess, Friedreich ataxia, gracile syndrome,Hallervorden-Spatz disease, Wilson's disease, pulmonary hemosiderosis,hepatocellular carcinoma, cancer, hepatitis, cirrhosis of liver, pica,chronic renal failure, anemia of end-stage renal disease, insulinresistance, diabetes, atherosclerosis, neurodegenerative disorders,multiple sclerosis, Parkinson's disease, Huntington's disease,Alzheimer's disease, restless leg syndrome, rheumatoid arthritis, andmacular degeneration.

Accordingly, one aspect of the present invention relates to thetreatment or prevention of a HJV-related disorder (e.g. iron-relateddisorder), or a hepcidin related disorder, or BMP-related disorder(e.g., anemia of inflammatory states) by administering an effectiveamount of a soluble form of HJV protein, such as a HJV fusion protein(e.g. HJV.Fc) as disclosed herein, or the nucleic acid sequence encodingsuch HJV fusion protein to a subject to decrease at least one symptom ofthe HJV, hepcidin, or BMP-related disorder (e.g., anemia of inflammatorystates).

Increasing soluble HJV in a subject, such as administering a soluble HJVpolypeptide such as a HJV fusion protein as disclosed herein, oradministering a nucleic acid construct encoding such HJV fusion protein,in a subject in need thereof is expected to treat or otherwiseameliorate the symptoms of conditions and physical dysfunctionsdescribed herein (e.g., those arising from an HJV-related disorder suchas an iron-related disorder in the subject). As used herein, the term“treatment” refers to treating a condition that has already manifestedin the subject. Treatment is performed generally on a subject who issuffering from a condition or physical dysfunction. Such subjects aresaid to be in need of treatment. Manifestation of a condition would beby the appearance of one or more symptoms of the condition. Many suchconditions and symptoms of an HJV-related disorder, such as aniron-related disorder are described herein. Treatment is also used torefer to a slowing of onset and/or severity of additional symptomswherein the subject already has one or more symptoms. The skilledartisan will realize that complete cure is not necessary to qualify astreatment. As such, subjects suitable for treatment include those whoexhibit one or more symptoms of a condition and are at risk fordeveloping additional symptoms of a condition. Such subjects alsoinclude those with one or more symptoms of a condition, but who have notbeen diagnosed with the condition by a qualified medical professional.

In one embodiment, the methods of treatment described herein, furthercomprise selection of such a subject suffering from a condition (e.g.,one arising from iron deprivation or condition associated with a HJVdisorder or disease), or physical dysfunction as described herein, priorto administering a soluble HJV protein, such as a HJV fusion polypeptideas disclosed herein, to thereby treat the condition or dysfunction. Suchselection is performed by the skilled practitioner by a number ofavailable methods. For instance, assessment of symptoms which aredescribed herein.

Successful treatment is evidenced by amelioration of one or moresymptoms of the condition or dysfunction as discussed herein.

Increasing soluble HJV in a subject, such as administering a soluble HJVpolypeptide such as a HJV fusion protein as disclosed herein, oradministering a nucleic acid construct encoding such HJV fusion protein,in a subject in need thereof is expected to prevent or retard thedevelopment of the conditions and physical dysfunctions described herein(e.g., those arising from iron deprivation in the subject). The term“prevention” is used to refer to a situation wherein a subject does notyet have the specific condition being prevented, meaning that it has notmanifested in any appreciable form. Prevention encompasses prevention orslowing of onset and/or severity of a symptom, (including where thesubject already has one or more symptoms of another condition).Prevention is performed generally in a subject who is at risk fordevelopment of a condition or physical dysfunction. Such subjects aresaid to be in need of prevention.

In one embodiment, the methods of prevention described herein, furthercomprise selection of such a subject at risk for a condition (e.g., onearising from iron deprivation or a condition associated with aHJV-related disorder or disease), or physical dysfunction as describedherein, prior to administering a soluble HJV polypeptide such as a HJVfusion protein as disclosed herein, in the subject, to thereby preventthe condition or dysfunction. Such selection is performed by the skilledpractitioner by a number of available methods. For instance, assessmentof risk factors or diagnosis of a disease which is known to cause thecondition or dysfunction, or treatment or therapy known to cause thecondition or dysfunction. Subjects which have a disease or injury or arelevant family history which is known to contribute to the conditionare generally considered to be at increased risk. For example, subjectswhich a disease causing mutation in HJV sequence (Lanzara et al, 2004,Blood 103, 4317-4317 and Papanikolaou et al, 2004, Nat Genetics, 36;77-81) or a G320V mutation in HJV (Zhang et al, 2005; JBC, 280;33885-33894), or subjects with mutations in HFE, Tfr2 (encodingtransferrin receptor 2), SLC401A (encoding ferroportin), HAMP (encodinghepcidin), which are well known in the art and disclosed in Yang et al,Biochem, 2008, 47; 4237-4245, which is incorporated herein by reference.

In one embodiment of the invention, the subject is also undergoinganother therapy. Such therapies include, without limitation, othertherapies to treat or prevent the condition arising from irondeprivation. Such therapies are commonly known by persons of ordinaryskill in the art, and include but are not limited to iron supplements,vitamin B-12, folic acid and erythropoietin.

As used herein, the terms “treat” or “treatment” or “treating” refers toboth therapeutic treatment and prophylactic (i.e. preventative)measures, wherein the object is to prevent or slow the development ofthe disease, such as slow down the development of a tumor, the spread ofcancer, or reducing at least one effect or symptom of a condition,disease or disorder associated with inappropriate proliferation or acell mass, for example cancer. Treatment is generally “effective” if oneor more symptoms or clinical markers are reduced as that term is definedherein. Alternatively, treatment is “effective” if the progression of adisease is reduced or halted. That is, “treatment” includes not just theimprovement of symptoms or markers, but also a cessation of at leastslowing of progress or worsening of symptoms that would be expected inabsence of treatment. Beneficial or desired clinical results include,but are not limited to, alleviation of one or more symptom(s),diminishment of extent of disease, stabilized (i.e., not worsening)state of disease, delay or slowing of disease progression, ameliorationor palliation of the disease state, and remission (whether partial ortotal), whether detectable or undetectable. “Treatment” can also meanprolonging survival as compared to expected survival if not receivingtreatment. Those in need of treatment include those already diagnosedwith cancer, as well as those likely to develop secondary tumors due tometastasis.

The term “effective amount” as used herein refers to the amount of apharmaceutical composition comprising a soluble HJV protein, such as aHJV fusion protein as disclosed herein, to decrease at least one or moresymptom of the disease or disorder, and relates to a sufficient amountof pharmacological composition to provide the desired effect. The phrase“therapeutically effective amount” as used herein, e.g., soluble HJVprotein, such as a HJV fusion protein as disclosed herein means asufficient amount of the composition to treat a disorder, at areasonable benefit/risk ratio applicable to any medical treatment. Theterm “therapeutically effective amount” therefore refers to an amount ofthe composition as disclosed herein that is sufficient to effect atherapeutically or prophylatically significant reduction in a symptom orclinical marker associated with decreased iron levels when administeredto a typical subject who has anemia, anemia of inflammation orhypoferremia.

A therapeutically or prophylatically significant reduction in a symptomis, e.g. at least about 10%, at least about 20%, at least about 30%, atleast about 40%, at least about 50%, at least about 60%, at least about70%, at least about 80%, at least about 90%, at least about 100%, atleast about 125%, at least about 150% or more in a measured parameter ascompared to a control or non-treated subject. Measured or measurableparameters include clinically detectable markers of disease, forexample, elevated or depressed levels of a biological marker, as well asparameters related to a clinically accepted scale of symptoms or markersfor a disease or disorder. It will be understood, however, that thetotal daily usage of the compositions and formulations as disclosedherein will be decided by the attending physician within the scope ofsound medical judgment. The exact amount required will vary depending onfactors such as the type of disease being treated.

With reference to the treatment of a subject with anemia, the term“therapeutically effective amount” refers to the amount that is safe andsufficient to prevent or delay the development and further decrease inserum iron concentrations, or decrease in transferrin saturation inanemic patients. The amount can thus cure or cause a decrease in atleast one anemic symptom, or cause the anemia to go into remission, slowthe course of anemia progression. The effective amount for the treatmentof anemia depends on the type of anemia and other diseases or disorderscausing the anemia as a secondary disease (i.e. vitamin D12 deficiency,sickle cell anemia), the species being treated, the age and generalcondition of the subject, the mode of administration and so forth. Thus,it is not possible to specify the exact “effective amount”. However, forany given case, an appropriate “effective amount” can be determined byone of ordinary skill in the art using only routine experimentation. Theefficacy of treatment can be judged by an ordinarily skilledpractitioner, for example, efficacy can be assessed in animal models ofanemia, for example treatment an as disclosed herein in the Examples,administration to a rodent with low serum iron, and any treatment oradministration of the compositions or formulations that leads to anincrease in serum iron and/or increase in transferrin saturation (forexample by the methods as disclosed herein), and/or a decrease of atleast one symptom of associated with anemia, for example easy fatigueand loss of energy; rapid heart beat, particularly with exercise;shortness of breath and headache, particularly with exercise; difficultyconcentrating; dizziness; pale skin; leg cramps; pica (hunger forstrange substances such as paper, ice, or dirt); koilonychias (upwardcurvature of the nails); soreness of the mouth with cracks at thecorners, etc. indicates effective treatment. Other symptoms of anemiacan include; Black and tarry stools; Maroon or visibly bloody stools;rapid heart rate; rapid breathing; cold skin; jaundice; low bloodpressure; heart murmur and enlargement of the spleen. In embodimentswhere the compositions are used for the treatment of anemia, theefficacy of the composition can be judged using an experimental animalmodel of anemia, e.g., wild-type mice or rats that have anemia and/oriron deficiency, or as disclosed herein, 129S6/SvEvTac mice (Taconic)mice fed 380 parts per million iron; Fanconi Anemia Group C mouse model(Fac−/−); administration of IgM and IgA anti-erythrocyte auto-antibodiesto mice (Baudino et al., Blood, 2007, 109; 5355-5362), or HJV^(−/−) mice(Huang et al, 2005, J Clin Invest, 115, 2187-2119 (which is incorporatedherein in its entirety by reference). When using an experimental animalmodel, efficacy of treatment is evidenced when a reduction in a symptomof the anemia, for example an increase in the level of serum iron and/orincrease in transferrin saturation, increase of iron release fromreticuloendothelial stores, and/or an increase in ferroportinexpression, and/or increase in hepatic tissue iron which occurs earlierin treated, versus untreated animals. By “earlier” is meant that anincrease, for example in the serum iron concentration occurs at least 5%earlier, but preferably more, e.g., one day earlier, two days earlier, 3days earlier, or more.

As used herein, the term “treating” when used in reference to anemia isused to refer to the reduction of a symptom and/or a biochemical markerof anemia, for example a reduction in at least one biochemical marker ofanemia by at least about 10% would be considered an effective treatment.Examples of such biochemical markers of anemia include, but are notlimited to, hematological markers (hemoglobin (HGB), mean corpuscularvolume (MCV), mean corpuscular hemoglobin (MCH), red cell distributionwidth (RDW)) and biochemical markers (serum ferritin (SF), serum iron(SI), transferrin saturation (TS), total iron-binding capacity (TIBC)and reticulocyte hemoglobin content (CHr). As alternative examples,blood test for anemia may show a normal or low hemoglobin, decreasediron, ferritin, and all red blood cell indices. Thus, an increase inhemoglobin or iron or ferritin, or increase in number of red blood cellsby at least about 10% would also be considered as affective treatmentsby the methods as disclosed herein. One can measure blood hematocrit(the % of blood volume made up by red blood cells and hemoglobin).Normal levels of hemoglobin range between 11.1 and 15.0 grams perdeciliter (g/dL). A lower than normal hemoglobin level indicates anemia.For example, a women that has a level equal to, or less than 10 g/dL isconsidered to be anemic, and a male that has a level equal to, or lessthan 12 g/dL is considered to be anemic. Alternatively, the totaliron-binding capacity (TIBC) or transferrin will be increased in anemicsubjects, so a decrease in the total iron-binding capacity (TIBC) ortransferrin by at least about 10% would also be considered as affectivetreatments by the methods as disclosed herein. In some embodiments, itis preferred, but not required that the therapeutic agent actuallyeliminate the tumor.

As used herein, the terms “administering,” and “introducing” are usedinterchangeably herein and refer to the placement of the therapeuticagents such as the soluble HJV protein, such as HJV.Fc fusion protein asdisclosed herein into a subject by a method or route which results indelivering of such agent(s) at a desired site. The compounds can beadministered by any appropriate route which results in an effectivetreatment in the subject.

The HJV fusion protein or polynucleotide may be administered by anyroute known in the art or described herein, for example, oral,parenteral (e.g., intravenously or intramuscularly), intraperitoneal,rectal, cutaneous, nasal, vaginal, inhalant, skin (patch), or ocular.The HJV fusion protein may be administered in any dose or dosingregimen.

IV. Dosage

With respect to the therapeutic methods of the invention, it is notintended that the administration of the HJV fusion protein orpolynucleotide encoding such a protein be limited to a particular modeof administration, dosage, or frequency of dosing; the present inventioncontemplates all modes of administration, including intramuscular,intravenous, intraperitoneal, intravesicular, intraarticular,intralesional, subcutaneous, or any other route sufficient to provide adose adequate to treat the BMP, hepcidin, or HJV-related disorder. Thetherapeutic may be administered to the patient in a single dose or inmultiple doses. When multiple doses are administered, the doses may beseparated from one another by, for example, one hour, three hours, sixhours, eight hours, one day, two days, one week, two weeks, or onemonth. For example, the therapeutic may be administered for, e.g., 2, 3,4, 5, 6, 7, 8, 10, 15, 20, or more weeks. It is to be understood that,for any particular subject, specific dosage regimes should be adjustedover time according to the individual need and the professional judgmentof the person administering or supervising the administration of thecompositions. For example, the dosage of the therapeutic can beincreased if the lower dose does not provide sufficient therapeuticactivity.

While the attending physician ultimately will decide the appropriateamount and dosage regimen, therapeutically effective amounts of the HJVfusion protein may provided at a dose of 0.0001, 0.01, 0.01 0.1, 1, 5,10, 25, 50, 100, 500, or 1,000 mg/kg. Effective doses may beextrapolated from dose-response curves derived from in vitro or animalmodel test bioassays or systems.

Dosages for a particular patient or subject can be determined by one ofordinary skill in the art using conventional considerations, (e.g. bymeans of an appropriate, conventional pharmacological protocol). Aphysician may, for example, prescribe a relatively low dose at first,subsequently increasing the dose until an appropriate response isobtained. The dose administered to a patient is sufficient to effect abeneficial therapeutic response in the patient over time, or, e.g., toreduce symptoms, or other appropriate activity, depending on theapplication. The dose is determined by the efficacy of the particularformulation, and the activity, stability or serum half-life of thesoluble HJV protein, such as HJV fusion protein as disclosed herein, orfunctional derivatives thereof, and the condition of the patient, aswell as the body weight or surface area of the patient to be treated.The size of the dose is also determined by the existence, nature, andextent of any adverse side-effects that accompany the administration ofa particular vector, formulation, or the like in a particular subject.Therapeutic compositions comprising soluble HJV proteins, such as HJVfusion proteins or functional derivatives thereof are optionally testedin one or more appropriate in vitro and/or in vivo animal models ofdisease, such as models of anemia or anemia of chronic disease (ACD), toconfirm efficacy, tissue metabolism, and to estimate dosages, accordingto methods well known in the art. In particular, dosages can beinitially determined by activity, stability or other suitable measuresof treatment vs. non-treatment (e.g., comparison of treated vs.untreated cells or animal models), in a relevant assay. Formulations areadministered at a rate determined by the LD50 of the relevantformulation, and/or observation of any side-effects of a soluble HJVprotein, such as HJV fusion protein or functional derivatives thereof atvarious concentrations, e.g., as applied to the mass and overall healthof the patient. Administration can be accomplished via single or divideddoses.

In determining the effective amount of a soluble HJV protein, such asHJV fusion protein or functional derivatives thereof to be administeredin the treatment or prophylaxis of disease the physician evaluatescirculating plasma levels, formulation toxicities, and progression ofthe disease.

The efficacy and toxicity of the compound can be determined by standardpharmaceutical procedures in cell cultures or experimental animals,e.g., ED50 (the dose is effective in 50% of the population) and LD50(the dose is lethal to 50% of the population). The dose ratio of toxicto therapeutic effects is the therapeutic index, and it can be expressedas the ratio, LD50/ED50. Pharmaceutical compositions which exhibit largetherapeutic indices are preferred.

These compounds may be administered to humans and other animals fortherapy by any suitable route of administration, including orally,nasally, as by, for example, a spray, rectally, intravaginally,parenterally, intracisternally and topically, as by powders, ointmentsor drops, including buccally and sublingually.

Actual dosage levels of the active ingredients in the pharmaceuticalcompositions of this invention may be varied so as to obtain an amountof the active ingredient which is effective to achieve the desiredtherapeutic response for a particular subject, composition, and mode ofadministration, without being toxic to the subject.

The selected dosage level will depend upon a variety of factorsincluding the activity of the particular compound of the presentinvention employed, or the ester, salt or amide thereof, the route ofadministration, the time of administration, the rate of excretion of theparticular compound being employed, the duration of the treatment, otherdrugs, compounds and/or materials used in combination with theparticular compound employed, the age, sex, weight, condition, generalhealth and prior medical history of the patient being treated, and likefactors well known in the medical arts.

VII. Formulation of Pharmaceutical Compositions

The administration of an HJV fusion protein may be by any suitable meansthat results in a concentration of the protein that treats the disorder.The compound may be contained in any appropriate amount in any suitablecarrier substance, and is generally present in an amount of 1-95% byweight of the total weight of the composition. The composition may beprovided in a dosage form that is suitable for the oral, parenteral(e.g., intravenously or intramuscularly), intraperitoneal, rectal,cutaneous, nasal, vaginal, inhalant, skin (patch), or ocularadministration route. Thus, the composition may be in the form of, e.g.,tablets, capsules, pills, powders, granulates, suspensions, emulsions,solutions, gels including hydrogels, pastes, ointments, creams,plasters, drenches, osmotic delivery devices, suppositories, enemas,injectables, implants, sprays, or aerosols. The pharmaceuticalcompositions may be formulated according to conventional pharmaceuticalpractice (see, e.g., Remington: The Science and Practice of Pharmacy,20th edition, 2000, ed. A. R. Gennaro, Lippincott Williams & Wilkins,Philadelphia, and Encyclopedia of Pharmaceutical Technology, eds. J.Swarbrick and J. C. Boylan, 1988-1999, Marcel Dekker, New York).

Pharmaceutical compositions according to the invention may be formulatedto release the active compound immediately upon administration or at anypredetermined time or time period after administration. The latter typesof compositions are generally known as controlled release formulations,which include (i) formulations that create substantially constantconcentrations of the agent(s) of the invention within the body over anextended period of time; (ii) formulations that after a predeterminedlag time create substantially constant concentrations of the agent(s) ofthe invention within the body over an extended period of time; (iii)formulations that sustain the agent(s) action during a predeterminedtime period by maintaining a relatively constant, effective level of theagent(s) in the body with concomitant minimization of undesirable sideeffects associated with fluctuations in the plasma level of the agent(s)(sawtooth kinetic pattern); (iv) formulations that localize action ofagent(s), e.g., spatial placement of a controlled release compositionadjacent to or in the diseased tissue or organ; (v) formulations thatachieve convenience of dosing, e.g., administering the composition onceper week or once every two weeks; and (vi) formulations that target theaction of the agent(s) by using carriers or chemical derivatives todeliver the therapeutic to a particular target cell type. Administrationof the protein in the form of a controlled release formulation isespecially preferred for compounds having a narrow absorption window inthe gastrointestinal tract or a relatively short biological half-life.

Any of a number of strategies can be pursued in order to obtaincontrolled release in which the rate of release outweighs the rate ofmetabolism of the compound in question. In one example, controlledrelease is obtained by appropriate selection of various formulationparameters and ingredients, including, e.g., various types of controlledrelease compositions and coatings. Thus, the protein is formulated withappropriate excipients into a pharmaceutical composition that, uponadministration, releases the protein in a controlled manner. Examplesinclude single or multiple unit tablet or capsule compositions, oilsolutions, suspensions, emulsions, microcapsules, molecular complexes,microspheres, nanoparticles, patches, and liposomes. As used herein, theterms “administering,” and “introducing” are used interchangeably hereinand refer to the placement of the therapeutic agents as disclosed hereininto a subject by a method or route which results in delivering of suchagent(s) at a desired site. The compounds can be administered by anyappropriate route which results in an effective treatment in thesubject.

As used herein, the phrases “parenteral administration” and“administered parenterally” as used herein mean modes of administrationother than enteral and topical administration, usually by injection, andincludes, without limitation, intravenous, intramuscular, intraarterial,intrathecal, intraventricular, intracapsular, intraorbital,intracardiac, intradermal, intraperitoneal, transtracheal, subcutaneous,subcuticular, intraarticular, sub capsular, subarachnoid, intraspinal,intracerebro spinal, and intrasternal injection and infusion. Thephrases “systemic administration,” “administered systemically”,“peripheral administration” and “administered peripherally” as usedherein mean the administration therapeutic compositions other thandirectly into a tumor such that it enters the animal's system and, thus,is subject to metabolism and other like processes.

The phrase “pharmaceutically acceptable” is employed herein to refer tothose compounds, materials, compositions, and/or dosage forms which are,within the scope of sound medical judgment, suitable for use in contactwith the tissues of human beings and animals without excessive toxicity,irritation, allergic response, or other problem or complication,commensurate with a reasonable benefit/risk ratio. The phrase“pharmaceutically acceptable carrier” as used herein means apharmaceutically acceptable material, composition or vehicle, such as aliquid or solid filler, diluent, excipient, solvent or encapsulatingmaterial, involved in maintaining the activity of or carrying ortransporting the subject agents from one organ, or portion of the body,to another organ, or portion of the body. In addition to being“pharmaceutically acceptable” as that term is defined herein, eachcarrier must also be “acceptable” in the sense of being compatible withthe other ingredients of the formulation. The pharmaceutical formulationcomprising the soluble HJV proteins, such as HJV fusion proteins asdisclosed herein in combination with one or more pharmaceuticallyacceptable ingredients. The carrier can be in the form of a solid,semi-solid or liquid diluent, cream or a capsule. These pharmaceuticalpreparations are a further object of the invention. Usually the amountof active compounds is between 0.1-95% by weight of the preparation,preferably between 0.2-20% by weight in preparations for parenteral useand preferably between 1 and 50% by weight in preparations for oraladministration. For the clinical use of the methods of the presentinvention, targeted delivery composition of the invention is formulatedinto pharmaceutical compositions or pharmaceutical formulations forparenteral administration, e.g., intravenous; mucosal, e.g., intranasal;enteral, e.g., oral; topical, e.g., transdermal; ocular, e.g., viacorneal scarification or other mode of administration. Thepharmaceutical composition contains a compound of the invention incombination with one or more pharmaceutically acceptable ingredients.The carrier can be in the form of a solid, semi-solid or liquid diluent,cream or a capsule.

The term “pharmaceutically acceptable carriers” is intended to includeall solvents, diluents, or other liquid vehicle, dispersion orsuspension aids, surface active agents, isotonic agents, thickening oremulsifying agents, preservatives, solid binders, lubricants and thelike, as suited to the particular dosage form desired. Typically, suchcompounds are carried or transported from one organ, or portion of thebody, to another organ, or portion of the body. Each carrier must be“acceptable” in the sense of being compatible with the other ingredientsof the formulation and not injurious to the patient. Some examples ofmaterials which can serve as pharmaceutically acceptable carriersinclude: sugars, such as lactose, glucose and sucrose; starches, such ascorn starch and potato starch; cellulose, and its functionalderivatives, such as sodium carboxymethyl cellulose, ethyl cellulose andcellulose acetate; powdered tragacanth; malt; gelatin; talc; excipients,such as cocoa butter and suppository waxes; oils, such as peanut oil,cottonseed oil, safflower oil, sesame oil, olive oil, corn oil andsoybean oil; glycols, such as propylene glycol; polyols, such asglycerin, sorbitol, mannitol and polyethylene glycol; esters, such asethyl oleate and ethyl laurate; agar; buffering agents, such asmagnesium hydroxide and aluminum hydroxide; alginic acid; pyrogen-freewater; isotonic saline; Ringer's solution; ethyl alcohol; phosphatebuffer solutions; and other non-toxic compatible substances employed inpharmaceutical formulations.

The terms “composition” or “pharmaceutical composition” usedinterchangeably herein refer to compositions or formulations thatusually comprise an excipient, such as a pharmaceutically acceptablecarrier that is conventional in the art and that is suitable foradministration to mammals, and preferably humans or human cells. Suchcompositions can be specifically formulated for administration via oneor more of a number of routes, including but not limited to, oral,ocular parenteral, intravenous, intraarterial, subcutaneous, intranasal,sublingual, intraspinal, intracerebroventricular, and the like. Inaddition, compositions for topical (e.g., oral mucosa, respiratorymucosa) and/or oral administration can form solutions, suspensions,tablets, pills, capsules, sustained-release formulations, oral rinses,or powders, as known in the art are described herein. The compositionsalso can include stabilizers and preservatives. For examples ofcarriers, stabilizers and adjuvants, University of the Sciences inPhiladelphia (2005) Remington: The Science and Practice of Pharmacy withFacts and Comparisons, 21st Ed. In certain embodiments, the compounds ofthe present invention may contain one or more acidic functional groupsand, thus, are capable of forming pharmaceutically acceptable salts withpharmaceutically acceptable bases. The term “pharmaceutically acceptablesalts, esters, amides, and prodrugs as used herein refers to thosecarboxylate salts, amino acid addition salts, esters, amides, andprodrugs of the compounds of the present invention which are, within thescope of sound medical judgment, suitable for use in contact with thetissues of patients without undue toxicity, irritation, allergicresponse, and the like, commensurate with a reasonable benefit/riskratio, and effective for their intended use of the compounds of theinvention. The term “salts” refers to the relatively non-toxic,inorganic and organic acid addition salts of compounds of the presentinvention. These salts can be prepared in situ during the finalisolation and purification of the compounds or by separately reactingthe purified compound in its free base form with a suitable organic orinorganic acid and isolating the salt thus formed. These may includecations based on the alkali and alkaline earth metals, such as sodium,lithium, potassium, calcium, magnesium and the like, as well asnon-toxic ammonium, quaternary ammonium, and amine cations including,but not limited to ammonium, tetramethylanunonium, tetraethyl ammonium,methyl amine, dimethyl amine, trimethylamine, triethylamine, ethylamine,and the like (see, e.g., Berge S. M., et al. (1977) J. Pharm. Sci. 66,1, which is incorporated herein by reference).

The term “pharmaceutically acceptable esters” refers to the relativelynon-toxic, esterified products of the compounds of the presentinvention. These esters can be prepared in situ during the finalisolation and purification of the compounds, or by separately reactingthe purified compound in its free acid form or hydroxyl with a suitableesterifying agent. Carboxylic acids can be converted into esters viatreatment with an alcohol in the presence of a catalyst. The term isfurther intended to include lower hydrocarbon groups capable of beingsolvated under physiological conditions, e.g., alkyl esters, methyl,ethyl and propyl esters.

As used herein, “pharmaceutically acceptable salts or prodrugs are saltsor prodrugs that are, within the scope of sound medical judgment,suitable for use in contact with the tissues of subject without unduetoxicity, irritation, allergic response, and the like, commensurate witha reasonable benefit/risk ratio, and effective for their intended use.

The term “prodrug” refers to compounds that are rapidly transformed invivo to yield the functionally active soluble HJV proteins, such as HJVfusion molecules of the present invention, for example the HJV fusionprotein of the invention could be hydrolyzed by the blood to render afully functional soluble form of HJV protein. A thorough discussion isprovided in T. Higachi and V. Stella, “Pro-drugs as Novel DeliverySystems,” Vol. 14 of the A.C.S. Symposium Series, and in BioreversibleCarriers in: Drug Design, ed. Edward B. Roche, American PharmaceuticalAssociation and Pergamon Press, 1987, both of which are herebyincorporated by reference. As used herein, a prodrug is a compound that,upon in vivo administration, is metabolized or otherwise converted tothe biologically, pharmaceutically or therapeutically active form of thecompound. A prodrug of the soluble HJV can be designed to alter themetabolic stability or the transport characteristics of a soluble HJVprotein, to mask side effects or toxicity, to improve the flavor of acompound or to alter other characteristics or properties of a compound.By virtue of knowledge of pharmacodynamic processes and drug metabolismin vivo, once a pharmaceutically active form of the HJV protein, such asderivatives and variants thereof, those of skill in the pharmaceuticalart generally can design prodrugs of the compound (see, e.g., Nogrady(1985) Medicinal Chemistry A Biochemical Approach, Oxford UniversityPress, N.Y., pages 388-392). Conventional procedures for the selectionand preparation of suitable prodrugs are described, for example, in“Design of Prodrugs,” ed. H. Bundgaard, Elsevier, 1985. Suitableexamples of prodrugs include methyl, ethyl and glycerol esters of thecorresponding acid.

a. Parenteral Compositions

The pharmaceutical composition may be administered parenterally byinjection, infusion, or implantation (subcutaneous, intravenous,intramuscular, intraperitoneal, or the like) in dosage forms,formulations, or via suitable delivery devices or implants containingconventional, non-toxic pharmaceutically acceptable carriers andadjuvants. The formulation and preparation of such compositions are wellknown to those skilled in the art of pharmaceutical formulation.

Compositions for parenteral use may be provided in unit dosage forms(e.g., in single-dose ampoules), or in vials containing several dosesand in which a suitable preservative may be added (see below). Thecomposition may be in form of a solution, a suspension, an emulsion, aninfusion device, or a delivery device for implantation, or it may bepresented as a dry powder to be reconstituted with water or anothersuitable vehicle before use. Apart from the active agent(s), thecomposition may include suitable parenterally acceptable carriers and/orexcipients. The active agent(s) may be incorporated into microspheres,microcapsules, nanoparticles, liposomes, or the like for controlledrelease. Furthermore, the composition may include suspending,solubilizing, stabilizing, pH-adjusting agents, tonicity adjustingagents, and/or dispersing agents.

As indicated above, the pharmaceutical compositions according to theinvention may be in a form suitable for sterile injection. To preparesuch a composition, the suitable active agent(s) are dissolved orsuspended in a parenterally acceptable liquid vehicle. Among acceptablevehicles and solvents that may be employed are water, water adjusted toa suitable pH by addition of an appropriate amount of hydrochloric acid,sodium hydroxide or a suitable buffer, 1,3-butanediol, Ringer'ssolution, dextrose solution, and isotonic sodium chloride solution. Theaqueous formulation may also contain one or more preservatives (e.g.,methyl, ethyl or n-propyl p-hydroxybenzoate). In cases where one of thecompounds is only sparingly or slightly soluble in water, a dissolutionenhancing or solubilizing agent can be added, or the solvent may include10-60% w/w of propylene glycol or the like.

Wetting agents, emulsifiers and lubricants, such as sodium laurylsulfate and magnesium stearate, as well as coloring agents, releaseagents, coating agents, sweetening, flavoring and perfuming agents,preservatives and antioxidants can also be present in the compositions.

Examples of pharmaceutically acceptable antioxidants include: watersoluble antioxidants, such as ascorbic acid, cysteine hydrochloride,sodium bisulfate, sodium metabisulfate, sodium sulfite and the like;oil-soluble antioxidants, such as ascorbyl palmitate, butylatedhydroxyanisole (BHA), butylated hydroxytoluene (BHT), lecithin, propylgallate, alpha-tocopherol, and the like; and metal chelating agents,such as citric acid, ethylenediamine tetraacetic acid (EDTA), sorbitol,tartaric acid, phosphoric acid, and the like.

Formulations of the present invention include those suitable forintravenous, oral, nasal, topical, transdermal, buccal, sublingual,rectal, vaginal and/or parenteral administration. The formulations mayconveniently be presented in unit dosage form and may be prepared by anymethods well known in the art of pharmacy. The amount of activeingredient which can be combined with a carrier material to produce asingle dosage form will generally be that amount of the compound whichproduces a therapeutic effect.

Methods of preparing these formulations or compositions include the stepof bringing into association a compound of the present invention withthe carrier and, optionally, one or more accessory ingredients. Ingeneral, the formulations are prepared by uniformly and intimatelybringing into association a compound of the present invention withliquid carriers, or finely divided solid carriers, or both, and then, ifnecessary, shaping the product.

Formulations of the invention suitable for oral administration may be inthe form of capsules, cachets, pills, tablets, lozenges (using aflavored basis, usually sucrose and acacia or tragacanth), powders,granules, or as a solution or a suspension in an aqueous or non-aqueousliquid, or as an oil-in-water or water-in-oil liquid emulsion, or as anelixir or syrup, or as pastilles (using an inert base, such as gelatinand glycerin, or sucrose and acacia) and/or as mouth washes and thelike, each containing a predetermined amount of a compound of thepresent invention as an active ingredient. A compound of the presentinvention may also be administered as a bolus, electuary or paste.

Pharmaceutical compositions of this invention suitable for parenteraladministration comprise one or more soluble HJV proteins, such as HJVfusion proteins as disclosed herein in combination with one or morepharmaceutically acceptable sterile isotonic aqueous or nonaqueoussolutions, dispersions, suspensions or emulsions, or sterile powderswhich may be reconstituted into sterile injectable solutions ordispersions just prior to use, which may contain antioxidants, buffers,bacteriostats, solutes which render the formulation isotonic with theblood of the intended recipient or suspending or thickening agents.

Examples of suitable aqueous and nonaqueous carriers which may beemployed in the pharmaceutical compositions comprising soluble HJVprotein, such as HJV fusion protein as disclosed herein include water,ethanol, polyols (such as glycerol, propylene glycol, polyethyleneglycol, and the like), and suitable mixtures thereof, vegetable oils,such as olive oil, and injectable organic esters, such as ethyl oleate.Proper fluidity can be maintained, for example, by the use of coatingmaterials, such as lecithin, by the maintenance of the required particlesize in the case of dispersions, and by the use of surfactants.

These compositions can also contain adjuvants such as preservatives,wetting agents, emulsifying agents and dispersing agents. Prevention ofthe action of microorganisms may be ensured by the inclusion of variousantibacterial and antifungal agents, for example, paraben,chlorobutanol, phenol sorbic acid, and the like. It may also bedesirable to include isotonic agents, such as sugars, sodium chloride,and the like into the compositions. In addition, prolonged absorption ofthe injectable pharmaceutical form may be brought about by the inclusionof agents which delay absorption such as aluminum monostearate andgelatin.

In some cases, in order to prolong the effect of a drug, it is desirableto slow the absorption of the drug from subcutaneous or intramuscularinjection. This may be accomplished by the use of a liquid suspension ofcrystalline or amorphous material having poor water solubility. The rateof absorption of the drug then depends upon its rate of dissolutionwhich, in turn, may depend upon crystal size and crystalline form.Alternatively, delayed absorption of a parenterally-administered drugform is accomplished by dissolving or suspending the drug in an oilvehicle.

Injectable depot forms are made by forming microencapsulated matrices ofthe subject compounds in biodegradable polymers such aspolylactide-polyglycolide. Depending on the ratio of drug to polymer,and the nature of the particular polymer employed, the rate of drugrelease can be controlled. Examples of other biodegradable polymersinclude poly(orthoesters) and poly(anhydrides). Depot injectableformulations are also prepared by entrapping the drug, such as solubleHJV protein, such as HJV fusion protein as disclosed herein in liposomesor microemulsions which are compatible with body tissue.

Regardless of the route of administration selected, the compounds of thepresent invention, which may be used in a suitable hydrated form, and/orthe pharmaceutical compositions of the present invention, are formulatedinto pharmaceutically acceptable dosage forms by conventional methodsknown to those of ordinary skill in the art.

b. Controlled Release Parenteral Compositions

Controlled release parenteral compositions may be in form of aqueoussuspensions, microspheres, microcapsules, magnetic microspheres, oilsolutions, oil suspensions, or emulsions. The composition may also beincorporated in biocompatible carriers, liposomes, nanoparticles,implants, or infusion devices.

Materials for use in the preparation of microspheres and/ormicrocapsules are, e.g., biodegradable/bioerodible polymers such aspolygalactin, poly-(isobutyl cyanoacrylate),poly(2-hydroxyethyl-L-glutamine), poly(lactic acid), polyglycolic acid,and mixtures thereof. Biocompatible carriers that may be used whenformulating a controlled release parenteral formulation arecarbohydrates (e.g., dextrans), proteins (e.g., albumin), lipoproteins,or antibodies. Materials for use in implants can be non-biodegradable(e.g., polydimethyl siloxane) or biodegradable (e.g.,poly(caprolactone), poly(lactic acid), poly(glycolic acid) or poly(orthoesters)) or combinations thereof.

c. Solid Dosage Forms for Oral Use

Formulations for oral use include tablets containing the activeingredient(s) in a mixture with non-toxic pharmaceutically acceptableexcipients, and such formulations are known to the skilled artisan(e.g., U.S. Pat. Nos. 5,817,307, 5,824,300, 5,830,456, 5,846,526,5,882,640, 5,910,304, 6,036,949, 6,036,949, 6,372,218, herebyincorporated by reference). These excipients may be, for example, inertdiluents or fillers (e.g., sucrose, sorbitol, sugar, mannitol,microcrystalline cellulose, starches including potato starch, calciumcarbonate, sodium chloride, lactose, calcium phosphate, calcium sulfate,or sodium phosphate); granulating and disintegrating agents (e.g.,cellulose derivatives including microcrystalline cellulose, starchesincluding potato starch, croscarmellose sodium, alginates, or alginicacid); binding agents (e.g., sucrose, glucose, sorbitol, acacia, alginicacid, sodium alginate, gelatin, starch, pregelatinized starch,microcrystalline cellulose, magnesium aluminum silicate,carboxymethylcellulose sodium, methylcellulose, hydroxypropylmethylcellulose, ethylcellulose, polyvinylpyrrolidone, or polyethyleneglycol); and lubricating agents, glidants, and anti-adhesives (e.g.,magnesium stearate, zinc stearate, stearic acid, silicas, hydrogenatedvegetable oils, or talc). Other pharmaceutically acceptable excipientscan be colorants, flavoring agents, plasticizers, humectants, bufferingagents, and the like.

The tablets may be uncoated or they may be coated by known techniques,optionally to delay disintegration and absorption in thegastrointestinal tract and thereby providing a sustained action over alonger period. The coating may be adapted to release the protein in apredetermined pattern (e.g., in order to achieve a controlled releaseformulation) or it may be adapted not to release the agent(s) untilafter passage of the stomach (enteric coating). The coating may be asugar coating, a film coating (e.g., based on hydroxypropylmethylcellulose, methylcellulose, methyl hydroxyethylcellulose,hydroxypropylcellulose, carboxymethylcellulose, acrylate copolymers,polyethylene glycols and/or polyvinylpyrrolidone), or an enteric coating(e.g., based on methacrylic acid copolymer, cellulose acetate phthalate,hydroxypropyl methylcellulose phthalate, hydroxypropyl methylcelluloseacetate succinate, polyvinyl acetate phthalate, shellac, and/orethylcellulose). Furthermore, a time delay material such as, e.g.,glyceryl monostearate or glyceryl distearate, may be employed.

The solid tablet compositions may include a coating adapted to protectthe composition from unwanted chemical changes, (e.g., chemicaldegradation prior to the release of the active substances). The coatingmay be applied on the solid dosage form in a similar manner as thatdescribed in Encyclopedia of Pharmaceutical Technology, supra.

The compositions of the invention may be mixed together in the tablet,or may be partitioned. In one example, a first agent is contained on theinside of the tablet, and a second agent is on the outside, such that asubstantial portion of the second agent is released prior to the releaseof the first agent.

Formulations for oral use may also be presented as chewable tablets, oras hard gelatin capsules wherein the active ingredient is mixed with aninert solid diluent (e.g., potato starch, lactose, microcrystallinecellulose, calcium carbonate, calcium phosphate, or kaolin), or as softgelatin capsules wherein the active ingredient is mixed with water or anoil medium, for example, peanut oil, liquid paraffin, or olive oil.Powders and granulates may be prepared using the ingredients mentionedabove under tablets and capsules in a conventional manner using, e.g., amixer, a fluid bed apparatus, or spray drying equipment.

In solid dosage forms of the invention for oral administration(capsules, tablets, pills, dragees, powders, granules and the like), theactive ingredient is mixed with one or more pharmaceutically acceptablecarriers, such as sodium citrate or dicalcium phosphate, and/or any ofthe following: fillers or extenders, such as starches, lactose, sucrose,glucose, mannitol, and/or silicic acid; binders, such as, for example,carboxymethylcellulose, alginates, gelatin, polyvinyl pyrrolidone,sucrose and/or acacia; humectants, such as glycerol; disintegratingagents, such as agar-agar, calcium carbonate, potato or tapioca starch,alginic acid, certain silicates, and sodium carbonate; solutionretarding agents, such as paraffin; absorption accelerators, such asquaternary ammonium compounds; wetting agents, such as, for example,cetyl alcohol and glycerol monostearate; absorbents, such as kaolin andbentonite clay; lubricants, such a talc, calcium stearate, magnesiumstearate, solid polyethylene glycols, sodium lauryl sulfate, andmixtures thereof; and coloring agents. In the case of capsules, tabletsand pills, the pharmaceutical compositions may also comprise bufferingagents. Solid compositions of a similar type may also be employed asfillers in soft and hard-filled gelatin capsules using such excipientsas lactose or milk sugars, as well as high molecular weight polyethyleneglycols and the like.

A tablet may be made by compression or molding, optionally with one ormore accessory ingredients. Compressed tablets may be prepared usingbinder (for example, gelatin or hydroxypropylmethyl cellulose),lubricant, inert diluent, preservative, disintegrant (for example,sodium starch glycolate or cross-linked sodium carboxymethyl cellulose),surface-active or dispersing agent. Molded tablets may be made bymolding in a suitable machine a mixture of the powdered compoundmoistened with an inert liquid diluent.

The tablets, and other solid dosage forms of the pharmaceuticalcompositions of the present invention, such as dragees, capsules, pillsand granules, may optionally be scored or prepared with coatings andshells, such as enteric coatings and other coatings well known in thepharmaceutical-formulating art. They may also be formulated so as toprovide slow or controlled release of the active ingredient thereinusing, for example, hydroxypropylmethyl cellulose in varying proportionsto provide the desired release profile, other polymer matrices,liposomes and/or microspheres. They may be sterilized by, for example,filtration through a bacteria-retaining filter, or by incorporatingsterilizing agents in the form of sterile solid compositions which canbe dissolved in sterile water, or some other sterile injectable mediumimmediately before use. These compositions may also optionally containopacifying agents and may be of a composition that they release theactive ingredient(s) only, or preferentially, in a certain portion ofthe gastrointestinal tract, optionally, in a delayed manner. Examples ofembedding compositions which can be used include polymeric substancesand waxes. The active ingredient can also be in micro-encapsulated form,if appropriate, with one or more of the above-described excipients. Inone aspect, a solution of resolvin and/or protectin or precursor oranalog thereof can be administered as eye drops for ocularneovascularization or ear drops to treat otitis.

Liquid dosage forms for oral administration of the compounds of theinvention include pharmaceutically acceptable emulsions, microemulsions,solutions, suspensions, syrups and elixirs.

In addition to the active ingredient, the liquid dosage forms maycontain inert diluents commonly used in the art, such as, for example,water or other solvents, solubilizing agents and emulsifiers, such asethyl alcohol, isopropyl alcohol, ethyl carbonate, ethyl acetate, benzylalcohol, benzyl benzoate, propylene glycol, 1,3-butylene glycol, oils(in particular, cottonseed, groundnut, corn, germ, olive, castor andsesame oils), glycerol, tetrahydrofuryl alcohol, polyethylene glycolsand fatty acid esters of sorbitan, and mixtures thereof. Besides inertdiluents, the oral compositions can also include adjuvants such aswetting agents, emulsifying and suspending agents, sweetening,flavoring, coloring, perfuming and preservative agents.

Suspensions, in addition to the active compounds, may contain suspendingagents as, for example, ethoxylated isostearyl alcohols, polyoxyethylenesorbitol and sorbitan esters, microcrystalline cellulose, aluminummetahydroxide, bentonite, agar-agar and tragacanth, and mixturesthereof.

Dosage forms for the topical or transdermal administration of thesoluble HJV protein, such as HJV fusion protein as disclosed hereininclude powders, sprays, ointments, pastes, creams, lotions, gels,solutions, patches and inhalants. The active compound may be mixed understerile conditions with a pharmaceutically acceptable carrier, and withany preservatives, buffers, or propellants which may be required.

The ointments, pastes, creams and gels may contain, in addition to anactive compound of this invention, excipients, such as animal andvegetable fats, oils, waxes, paraffins, starch, tragacanth, cellulosederivatives, polyethylene glycols, silicones, bentonites, silicic acid,talc and zinc oxide, or mixtures thereof. Powders and sprays cancontain, in addition to a compound of this invention, excipients such aslactose, talc, silicic acid, aluminum hydroxide, calcium silicates andpolyamide powder, or mixtures of these substances. Sprays canadditionally contain customary propellants, such aschlorofluorohydrocarbons and volatile unsubstituted hydrocarbons, suchas butane and propane.

Transdermal patches have the added advantage of providing controlleddelivery of the compounds (resolvins and/or protectins and/or precursorsor analogues thereof) of the present invention to the body. Such dosageforms can be made by dissolving or dispersing the compound in the propermedium. Absorption enhancers can also be used to increase the flux ofthe compound across the skin. The rate of such flux can be controlled byeither providing a rate controlling membrane or dispersing the activecompound in a polymer matrix or gel. In another aspect, biodegradable orabsorbable polymers can provide extended, often localized, release ofpolypeptide agents. The potential benefits of an increased half-life orextended release for a therapeutic agent are clear. A potential benefitof localized release is the ability to achieve much higher localizeddosages or concentrations, for greater lengths of time, relative tobroader systemic administration, with the potential to also avoidpossible undesirable side effects that may occur with systemicadministration.

Bioabsorbable polymeric matrix suitable for delivery of the soluble HJVpolypeptide, such as HJV fusion polypeptides as disclosed herein can beselected from a variety of synthetic bioabsorbable polymers, which aredescribed extensively in the literature. Such synthetic bioabsorbable,biocompatible polymers, which may release proteins over several weeks ormonths can include, for example, poly-α-hydroxy acids (e.g.polylactides, polyglycolides and their copolymers), polyanhydrides,polyorthoesters, segmented block copolymers of polyethylene glycol andpolybutylene terephtalate (Polyactive™), tyrosine derivative polymers orpoly(ester-amides). Suitable bioabsorbable polymers to be used inmanufacturing of drug delivery materials and implants are discussed e.g.in U.S. Pat. Nos. 4,968,317, 5,618,563, among others, and in “BiomedicalPolymers” edited by S. W. Shalaby, Carl Hanser Verlag, Munich, Vienna,New York, 1994 and in many references cited in the above publications.The particular bioabsorbable polymer that should be selected will dependupon the particular patient that is being treated.

VII. Gene Therapy

An HJV fusion protein can be effectively used in treatment by genetherapy. See, generally, for example, U.S. Pat. No. 5,399,346, which isincorporated herein by reference. The general principle is to introducethe polynucleotide into a target cell in a patient, and allow it tosupplement the activity of the endogenous HJV protein.

Entry into the cell is facilitated by suitable techniques known in theart such as providing the polynucleotide in the form of a suitablevector, or encapsulation of the polynucleotide in a liposome.

A desired mode of gene therapy is to provide the polynucleotide in sucha way that it will replicate inside the cell, enhancing and prolongingthe desired effect. Thus, the polynucleotide is operably linked to asuitable promoter, such as the natural promoter of the correspondinggene, a heterologous promoter that is intrinsically active in liver,neuronal, bone, muscle, skin, joint, or cartilage cells, or aheterologous promoter that can be induced by a suitable agent.

Expression vectors compatible with eukaryotic cells, preferably thosecompatible with vertebrate cells, can be used to produce recombinantconstructs for the expression of soluble HJV proteins such as HJV fusionproteins as disclosed herein, including fusion proteins with fragmentsor derivatives or variants of HJV thereof as described herein.Eukaryotic cell expression vectors are well known in the art and areavailable from several commercial sources. Typically, such vectors areprovided containing convenient restriction sites for insertion of thedesired DNA segment. These vectors can be viral vectors such asadenovirus, adeno-associated virus, pox virus such as an orthopox(vaccinia and attenuated vaccinia), avipox, lentivirus, murine moloneyleukemia virus, etc. Alternatively, plasmid expression vectors can beused.

Viral vector systems which can be utilized in the present inventioninclude, but are not limited to, (a) adenovirus vectors; (b) retrovirusvectors; (c) adeno-associated virus vectors; (d) herpes simplex virusvectors; (e) SV 40 vectors; (f) polyoma virus vectors; (g) papillomavirus vectors; (h) picornavirus vectors; (i) pox virus vectors such asan orthopox, e.g., vaccinia virus vectors or avipox, e.g. canary pox orfowl pox; and (j) a helper-dependent or gutless adenovirus. In apreferred embodiment, the vector is an adenovirus. Replication-defectiveviruses can also be advantageous.

The vector may or may not be incorporated into the cells genome. Theconstructs may include viral sequences for transfection, if desired.Alternatively, the construct may be incorporated into vectors capable ofepisomal replication, e.g EPV and EBV vectors.

Constructs for the recombinant expression of soluble HJV proteins suchas HJV fusion proteins as disclosed herein (including fusion proteinswith fragments or derivatives or variants of HJV thereof) will generallyrequire regulatory elements, e.g., promoters, enhancers, etc., to ensurethe expression of the construct in target cells. Other specifics forvectors and constructs are described in further detail below.

By “operably linked” is meant that a nucleic acid molecule and one ormore regulatory sequences (e.g., a promoter) are connected in such a wayas to permit expression and/or secretion of the product (e.g., aprotein) of the nucleic acid molecule when the appropriate molecules(e.g., transcriptional activator proteins) are bound to the regulatorysequences. Stated another way, the term “operatively linked” as usedherein refers to the functional relationship of the nucleic acidsequences with regulatory sequences of nucleotides, such as promoters,enhancers, transcriptional and translational stop sites, and othersignal sequences. For example, operative linkage of nucleic acidsequences, typically DNA, to a regulatory sequence or promoter regionrefers to the physical and functional relationship between the DNA andthe regulatory sequence or promoter such that the transcription of suchDNA is initiated from the regulatory sequence or promoter, by an RNApolymerase that specifically recognizes, binds and transcribes the DNA.In order to optimize expression and/or in vitro transcription, it may benecessary to modify the regulatory sequence for the expression of thenucleic acid or DNA in the cell type for which it is expressed. Thedesirability of, or need of, such modification may be empiricallydetermined. An operatively linked polynucleotide which is to beexpressed typically includes an appropriate start signal (e.g., ATG) andmaintains the correct reading frame to permit expression of thepolynucleotide sequence under the control of the expression controlsequence, and production of the desired polypeptide encoded by thepolynucleotide sequence.

As used herein, the terms “promoter” or “promoter region” or “promoterelement” have been defined herein, refers to a segment of a nucleic acidsequence, typically but not limited to DNA or RNA or analogues thereof,that controls the transcription of the nucleic acid sequence to which itis operatively linked. The promoter region includes specific sequencesthat are sufficient for RNA polymerase recognition, binding andtranscription initiation. This portion of the promoter region isreferred to as the promoter. In addition, the promoter region includessequences which modulate this recognition, binding and transcriptioninitiation activity of RNA polymerase. These sequences may be cis-actingor may be responsive to trans-acting factors. Promoters, depending uponthe nature of the regulation may be constitutive or regulated.

The term “regulatory sequences” is used interchangeably with “regulatoryelements” herein refers element to a segment of nucleic acid, typicallybut not limited to DNA or RNA or analogues thereof, that modulates thetranscription of the nucleic acid sequence to which it is operativelylinked, and thus act as transcriptional modulators. Regulatory sequencesmodulate the expression of gene and/or nucleic acid sequence to whichthey are operatively linked. Regulatory sequence often comprise“regulatory elements” which are nucleic acid sequences that aretranscription binding domains and are recognized by the nucleicacid-binding domains of transcriptional proteins and/or transcriptionfactors, repressors or enhancers etc. Typical regulatory sequencesinclude, but are not limited to, transcriptional promoters, induciblepromoters and transcriptional elements, an optional operate sequence tocontrol transcription, a sequence encoding suitable mRNA ribosomalbinding sites, and sequences to control the termination of transcriptionand/or translation. Included in the term “regulatory elements” arenucleic acid sequences such as initiation signals, enhancers, andpromoters, which induce or control transcription of protein codingsequences with which they are operatively linked. In some examples,transcription of a recombinant gene is under the control of a promotersequence (or other transcriptional regulatory sequence) which controlsthe expression of the recombinant gene in a cell-type in whichexpression is intended. It will also be understood that the recombinantgene can be under the control of transcriptional regulatory sequenceswhich are the same or which are different from those sequences whichcontrol transcription of the naturally-occurring form of a protein. Insome instances the promoter sequence is recognized by the syntheticmachinery of the cell, or introduced synthetic machinery, required forinitiating transcription of a specific gene.

Regulatory sequences can be a single regulatory sequence or multipleregulatory sequences, or modified regulatory sequences or fragmentsthereof. Modified regulatory sequences are regulatory sequences wherethe nucleic acid sequence has been changed or modified by some means,for example, but not limited to, mutation, methylation etc.

Regulatory sequences useful in the methods as disclosed herein arepromoter elements which are sufficient to render promoter-dependent geneexpression controllable for cell type-specific, tissue-specific orinducible by external signals or agents (e.g. enhancers or repressors);such elements may be located in the 5′ or 3′ regions of the native gene,or within an intron.

As used herein, the term “tissue-specific promoter” means a nucleic acidsequence that serves as a promoter, i.e., regulates expression of aselected nucleic acid sequence operably linked to the promoter, andwhich selectively affects expression of the selected nucleic acidsequence in specific cells of a tissue, such as cells of neural origin,e.g. neuronal cells.

In some embodiments, it can be advantageous to direct expression of asoluble HJV proteins such as HJV fusion proteins as disclosed herein(including fusion proteins with fragments or derivatives or variants ofHJV thereof as described herein) in a tissue- or cell-specific manner.Muscle-specific expression can be achieved, for example, using theskeletal muscle MKC promoter (as disclosed in U.S. Patent ApplicationWO2007/100722, which is incorporated herein by reference), or othermuscle-specific promoters, such as α-myosin heavy chain, myosin lightchain-2 (which is specific for skeletal muscle (Shani et al., Nature,314; 283-86, 1985), gonadotrophic releasing hormone gene control regionwhich is active in the hypothalamus (Mason et al, Science, 234; 1372-78,1986), and smooth muscle promoter SM22a, which are all commonly known inthe art.

The term “constitutively active promoter” refers to a promoter of a genewhich is expressed at all times within a given cell. Exemplary promotersfor use in mammalian cells include cytomegalovirus (CMV), and for use inprokaryotic cells include the bacteriophage T7 and T3 promoters, and thelike. The term “inducible promoter” refers to a promoter of a gene whichcan be expressed in response to a given signal, for example addition orreduction of an agent. Non-limiting examples of an inducible promoterare “tet-on” and “tet-off” promoters, or promoters that are regulated ina specific tissue type.

In a specific embodiment, viral vectors that contain nucleic acidsequences encoding the soluble HJV proteins, such as HJV fusion proteinsas disclosed herein (including fusion proteins with fragments orderivatives or variants of HJV thereof as described herein) are used.For example, a retroviral vector can be used (see Miller et al., Meth.Enzymol. 217:581-599 (1993)). These retroviral vectors contain thecomponents necessary for the correct packaging of the viral genome andintegration into the host cell DNA. The nucleic acid sequences encodinga human HJV fusion polypeptide are cloned into one or more vectors,which facilitates delivery of the gene into a patient. More detail aboutretroviral vectors can be found in Boesen et al., Biotherapy 6:291-302(1994), which describes the use of a retroviral vector to deliver themdr1 gene to hematopoietic stem cells in order to make the stem cellsmore resistant to chemotherapy. Other references illustrating the use ofretroviral vectors in gene therapy are: Clowes et al., J. Clin. Invest.93:644-651 (1994); Kiem et al., Blood 83:1467-1473 (1994); Salmons andGunzberg, Human Gene Therapy 4:129-141 (1993); and Grossman and Wilson,Curr. Opin. in Genetics and Devel. 3:110-114 (1993).

The production of a recombinant retroviral vector carrying a gene ofinterest is typically achieved in two stages. First, sequence encoding ahuman HJV fusion polypeptide can be inserted into a retroviral vectorwhich contains the sequences necessary for the efficient expression ofthe metabolic regulators (including promoter and/or enhancer elementswhich can be provided by the viral long terminal repeats (LTRs) or by aninternal promoter/enhancer and relevant splicing signals), sequencesrequired for the efficient packaging of the viral RNA into infectiousvirions (e.g., a packaging signal (Psi), a tRNA primer binding site(−PBS), a 3′ regulatory sequence required for reverse transcription(+PBS)), and a viral LTRs). The LTRs contain sequences required for theassociation of viral genomic RNA, reverse transcriptase and integrasefunctions, and sequences involved in directing the expression of thegenomic RNA to be packaged in viral particles.

Following the construction of the recombinant retroviral vector, thevector DNA is introduced into a packaging cell line. Packaging celllines provide viral proteins required in trans for the packaging ofviral genomic RNA into viral particles having the desired host range(e.g., the viral-encoded core (gag), polymerase (pol) and envelope (env)proteins). The host range is controlled, in part, by the type ofenvelope gene product expressed on the surface of the viral particle.Packaging cell lines can express ecotrophic, amphotropic or xenotropicenvelope gene products. Alternatively, the packaging cell line can lacksequences encoding a viral envelope (env) protein. In this case, thepackaging cell line can package the viral genome into particles whichlack a membrane-associated protein (e.g., an env protein). To produceviral particles containing a membrane-associated protein which permitsentry of the virus into a cell, the packaging cell line containing theretroviral sequences can be transfected with sequences encoding amembrane-associated protein (e.g., the G protein of vesicular stomatitisvirus (VSV)). The transfected packaging cell can then produce viralparticles which contain the membrane-associated protein expressed by thetransfected packaging cell line; these viral particles which containviral genomic RNA derived from one virus encapsidated by the envelopeproteins of another virus are said to be pseudotyped virus particles.

Adenoviruses are other viral vectors that can be used in gene therapy.Adenoviruses are especially attractive vehicles for delivering genes torespiratory epithelia. Adenoviruses naturally infect respiratoryepithelia where they cause a mild disease. Other targets foradenovirus-based delivery systems are liver, the central nervous system,endothelial cells, and muscle. Adenoviruses have the advantage of beingcapable of infecting non-dividing cells. Kozarsky and Wilson, CurrentOpinion in Genetics and Development 3:499-503 (1993) present a review ofadenovirus-based gene therapy. Bout et al., Human Gene Therapy 5:3-10(1994) demonstrated the use of adenovirus vectors to transfer genes tothe respiratory epithelia of rhesus monkeys. Another preferred viralvector is a pox virus such as a vaccinia virus, for example anattenuated vaccinia such as Modified Virus Ankara (MVA) or NYVAC, anavipox such as fowl pox or canary pox. Other instances of the use ofadenoviruses in gene therapy can be found in Rosenfeld et al., Science252:431-434 (1991); Rosenfeld et al., Cell 68:143-155 (1992);Mastrangeli et al., J. Clin. Invest. 91:225-234 (1993); PCT PublicationWO94/12649; and Wang, et al., Gene Therapy 2:775-783 (1995). In anotherembodiment, lentiviral vectors are used, such as the HIV based vectorsdescribed in U.S. Pat. Nos. 6,143,520; 5,665,557; and 5,981,276, whichare herein incorporated by reference. Use of Adeno-associated virus(AAV) vectors is also contemplated (Walsh et al., Proc. Soc. Exp. Biol.Med. 204:289-300 (1993); U.S. Pat. No. 5,436,146 which is incorporatedherein by reference).

Another approach to gene therapy involves transferring a gene to cellsin tissue culture by such methods as electroporation, lipofection,calcium phosphate mediated transfection, or viral infection. Usually,the method of transfer includes the transfer of a selectable marker tothe cells. The cells are then placed under selection to isolate thosecells that have taken up and are expressing the transferred gene. Thosecells are then delivered to a patient.

U.S. Pat. No. 5,676,954 (which is herein incorporated by reference)reports on the injection of genetic material, complexed with cationicliposome carriers, into mice. U.S. Pat. Nos. 4,897,355, 4,946,787,5,049,386, 5,459,127, 5,589,466, 5,693,622, 5,580,859, 5,703,055, andinternational publication NO: WO 94/9469 (which are herein incorporatedby reference) provide cationic lipids for use in transfecting DNA intocells and mammals. U.S. Pat. Nos. 5,589,466, 5,693,622, 5,580,859,5,703,055, and international publication NO: WO 94/9469 (which areherein incorporated by reference) provide methods for deliveringDNA-cationic lipid complexes to mammals. Such cationic lipid complexesor nanoparticles can also be used to deliver protein.

A gene or nucleic acid sequence can be introduced into a target cell byany suitable method. For example, an human HJV fusion polypeptideconstruct can be introduced into a cell by transfection (e.g., calciumphosphate or DEAE-dextran mediated transfection), lipofection,electroporation, microinjection (e.g., by direct injection of nakedDNA), biolistics, infection with a viral vector containing a musclerelated transgene, cell fusion, chromosome-mediated gene transfer,microcell-mediated gene transfer, nuclear transfer, and the like. Anucleic acid encoding an human HJV fusion polypeptide can be introducedinto cells by electroporation (see, e.g., Wong and Neumann, Biochem.Biophys. Res. Commun. 107:584-87 (1982)) and biolistics (e.g., a genegun; Johnston and Tang, Methods Cell Biol. 43 Pt A:353-65 (1994); Fynanet al., Proc. Natl. Acad. Sci. USA 90:11478-82 (1993)).

In certain embodiments, a gene or nucleic acid sequence encoding humanHJV fusion polypeptide can be introduced into target cells bytransfection or lipofection. Suitable agents for transfection orlipofection include, for example, calcium phosphate, DEAE dextran,lipofectin, lipfectamine, DIMRIE C, Superfect, and Effectin (Qiagen),unifectin, maxifectin, DOTMA, DOGS (Transfectam;dioctadecylamidoglycylspermine), DOPE(1,2-dioleoyl-sn-glycero-3-phosphoethanolamine), DOTAP(1,2-dioleoyl-3-trimethylammonium propane), DDAB (dimethyldioctadecylammonium bromide), DHDEAB(N,N-di-n-hexadecyl-N,N-dihydroxyethyl ammonium bromide), HDEAB(N-n-hexadecyl-N,N-dihydroxyethylammonium bromide), polybrene,poly(ethylenimine) (PEI), and the like. (See, e.g., Banerjee et al.,Med. Chem. 42:4292-99 (1999); Godbey et al., Gene Ther. 6:1380-88(1999); Kichler et al., Gene Ther. 5:855-60 (1998); Birchaa et al., J.Pharm. 183:195-207 (1999)).

Methods known in the art for the therapeutic delivery of agents such asproteins and/or nucleic acids can be used for the delivery of apolypeptide or nucleic acid encoding an human HJV fusion polypeptide formodulating iron metabolism and/or for increasing serum ironconcentration in a subject, e.g., cellular transfection, gene therapy,direct administration with a delivery vehicle or pharmaceuticallyacceptable carrier, indirect delivery by providing recombinant cellscomprising a nucleic acid encoding a targeting fusion polypeptide of theinvention.

Various delivery systems are known and can be used to directlyadminister therapeutic polypeptides such as the human HJV fusionpolypeptide and/or a nucleic acid encoding a human HJV fusionpolypeptide as disclosed herein, e.g., encapsulation in liposomes,microparticles, microcapsules, recombinant cells capable of expressingthe compound, and receptor-mediated endocytosis (see, e.g., Wu and Wu,1987, J. Biol. Chem. 262:4429-4432). Methods of introduction can beenteral or parenteral and include but are not limited to intradermal,intramuscular, intraperitoneal, intravenous, subcutaneous, pulmonary,intranasal, intraocular, epidural, and oral routes. The agents may beadministered by any convenient route, for example by infusion or bolusinjection, by absorption through epithelial or mucocutaneous linings(e.g., oral mucosa, rectal and intestinal mucosa, etc.) and may beadministered together with other biologically active agents.Administration can be systemic or local.

In a specific embodiment, it may be desirable to administer thepharmaceutical compositions of the invention locally to the area in needof treatment; this may be achieved, for example, and not by way oflimitation, by local infusion during surgery, topical application, e.g.,by injection, by means of a catheter, or by means of an implant, theimplant being of a porous, non-porous, or gelatinous material, includingmembranes, such as sialastic membranes, fibers, or commercial skinsubstitutes.

In another embodiment, the active agent can be delivered in a vesicle,in particular a liposome (see Langer (1990) Science 249:1527-1533). Inyet another embodiment, the active agent can be delivered in acontrolled release system. In one embodiment, a pump may be used (seeLanger (1990) supra). In another embodiment, polymeric materials can beused (see Howard et al. (1989) J. Neurosurg. 71:105).

Thus, a wide variety of gene transfer/gene therapy vectors andconstructs are known in the art. These vectors are readily adapted foruse in the methods of the present invention. By the appropriatemanipulation using recombinant DNA/molecular biology techniques toinsert an operatively linked human HJV fusion polypeptide encodingnucleic acid segment into the selected expression/delivery vector, manyequivalent vectors for the practice of the methods described herein canbe generated.

It will be appreciated by those of skill that cloned genes readily canbe manipulated to alter the amino acid sequence of a protein. The clonedgene for human HJV that comprise part of the HJV fusion polypeptide canbe manipulated by a variety of well known techniques for in vitromutagenesis, among others, to produce variants of the naturallyoccurring human protein, herein referred to as muteins or variants ormutants of HJV, which may be used in accordance with the methods andcompositions described herein.

The variation in primary structure of muteins of HJV useful in theinvention, for instance, may include deletions, additions andsubstitutions. The substitutions may be conservative ornon-conservative. The differences between the natural protein and themutein generally conserve desired properties, mitigate or eliminateundesired properties and add desired or new properties.

VIII. Other Embodiments

From the foregoing description, it will be apparent that variations andmodifications may be made to the invention described herein to adopt itto various usages and conditions. Such embodiments are also within thescope of the following claims.

The invention also contemplates an article of manufacture which is alabeled container for providing an soluble HJV protein such as a HJVfusion polypeptide as disclosed herein. An article of manufacturecomprises packaging material and a pharmaceutical agent of the solubleHJV polypeptide, such as a HJV fusion polypeptide, contained within thepackaging material.

The pharmaceutical agent in an article of manufacture is any of thecompositions of the present invention suitable for providing a solubleHJV protein, such as a HJV fusion polypeptide (e.g. HJV.Fc) andformulated into a pharmaceutically acceptable form as described hereinaccording to the disclosed indications. Thus, the composition cancomprise a HJV fusion polypeptide (e.g. HJV.Fc) or a DNA molecule whichis capable of expressing such a polypeptide.

The article of manufacture contains an amount of pharmaceutical agentsufficient for use in treating a condition indicated herein, either inunit or multiple dosages. The packaging material comprises a label whichindicates the use of the pharmaceutical agent contained therein, e.g.,for the treatment of a HJV-related disorder, such as an iron-relateddisorder as discussed herein, or for other indicated therapeutic orprophylactic uses.

The label can further include instructions for use and relatedinformation as may be required for marketing. The packaging material caninclude container(s) for storage of the pharmaceutical agent.

As used herein, the term packaging material refers to a material such asglass, plastic, paper, foil, and the like capable of holding withinfixed means a pharmaceutical agent. Thus, for example, the packagingmaterial can be plastic or glass vials, laminated envelopes and the likecontainers used to contain a pharmaceutical composition including thepharmaceutical agent.

In preferred embodiments, the packaging material includes a label thatis a tangible expression describing the contents of the article ofmanufacture and the use of the pharmaceutical agent contained therein.

IX. Materials and Methods

The following describes Materials and Methods useful not only for thestudies that elucidated the iron metabolism effects of a soluble form ofHJV, such as a HJV fusion protein as disclosed herein, but also for thepractice of the invention as described herein.

cDNA subcloning. The inventors generated cDNA encoding mutant mousehemojuvelin with a G313V substitution by an overlapping PCR strategyusing primers G313V-N-F, G313V-N-R, G313V-C-F and G313V-C-R, followed bysubcloning into pcDNA 3.1 (Invitrogen).

The inventors generated cDNA encoding soluble Hjv.Fc fusion protein byPCR of the extracellular domain of mouse hemojuvelin using the primersHjvECD-F and HjvECD-R, followed by subcloning into the mammalianexpression vector pIgplus (R & D Systems) in-frame with the Fc portionof human immunoglobulin.

The inventors generated cDNA encoding Flag-tagged human hemojuvelin(Flag-HJV) by using PCR to amplify human hemojuvelin transcript variantb, which does not contain exon 2, with primers HJVB-F and HJVB-R. Exon2, which codes for the signal peptide of the full-length hemojuvelintranscript variant a, was amplified by PCR from human genomic DNA usingthe primers HJVEx2-F and HJVEx2-R. The two overlapping fragments werefused together by PCR, and the full-length cDNA product was subclonedvia EcoRI/XhoI restriction sites into pcDNA3.1 (Invitrogen), to generatepcDNA3.1-HJV. To generate Flag-HJV, an upstream fragment correspondingto the beginning of exon 3 was generated by PCR using the primersHJVEx3-F and HJVEx3-R followed by digestion by NotI and SacII. Adownstream fragment was cut with SacII and XbaI from pcDNA3.1-HJV. Thetwo fragments were ligated and subcloned into the NotI and XbaI sites ofp3XFlag-CMV9 (Sigma) downstream of the preprotrypsin signal sequence andFlag tag.

cDNA encoding mutant Flag-tagged hemojuvelin with a valine to glycinesubstitution at amino acid 99 (Flag-G99V-HJV) was generated fromFlag-HJV by site-directed mutagenesis using the QuikChange kit(Stratagene).

cDNA encoding the hepcidin promoter luciferase construct was generatedby subcloning the −2649 to +45 region of the human hepcidin promoter46into the pGL2-Bsic vector (Promega) upstream of the firefly luciferasereporter gene.

All cDNAs were sequenced to verify the fidelity of the constructs(Massachusetts General Hospital Molecular Biology DNA Sequencing CoreFacility). See Table 1 for primer sequences.

TABLE 1 Primer sequences. Name Strand Sequence (5′ - 3′) G313V-N-F +ACCGAATTCGGGGGACCTGGCTGGATAG (SEQ ID NO: 12) G313V-N-R −CGGAGGGCATACCCCAACACACAG(SEQ ID NO: 13) G313V-C-F +CTGTGTGTTGGGGTATGCCCTCCG (SEQ ID NO: 14) G313V-C-R −CCCTCTAGATGGTGCCAGTCTCCAAAAGC (SEQ ID NO: 15) HjvECD-F +GGAAGCTTATGGGCCAGTCCCCTAGT (SEQ ID NO: 16) HjvECD-R −CCGGATCCGCTAAGTTCTCTAAATCCGTC (SEQ ID NO: 17) HJVB-F +CCTCTGTGGACATGCTCATTCTCAATGCAAGATCCTCCGCTG (SEQ ID NO: 18) HJVB-R −CGTCTCGAGTTACTGAATGCAAAGCCACAGAACAAAGAGC (SEQ ID NO: 19) HJVEx2-F +CGAGAATTCACTTACAGGGCTTCCGGTCA (SEQ ID NO: 20) HJVEx2-R −GCATTGAGAATGAGCATGTCCACAGAGGAGCAGCAG (SEQ ID NO: 21) HJVEx3-F +GACAGATCTGCGGCCGCTCATTCTCAATGCAAGATCCTCCG (SEQ ID NO: 22) HJVEx3-R −GAGCAGTTGTGCTGGATCATCAGG (SEQ ID NO: 23) HAMP-F +CTGCAACCCCAGGACAGAG (SEQ ID NO: 24) HAMP-R −GGAATAAATAAGGAAGGGAGGGG (SEQ ID NO: 25) ACTB-F +AGGATGCAGAAGGAGATCACTG (SEQ ID NO: 26) ACTB-R −GGGTGTAACGCAACTAAGTCATAG (SEQ ID NO: 27) BMP2-F +CGTGACCAGACTTTTGGACAC (SEQ ID NO: 28) BMP2-R −GGCATGATTAGTGGAGTTCAG (SEQ ID NO: 29) BMP4-F +AGCAGCCAAACTATGGGCTA (SEQ ID NO: 30) BMP4-R −TGGTTGAGTTGAGGTGGTCA (SEQ ID NO: 31) Hamp1-F +TCCTTAGACTGCACAGCAGAA (SEQ ID NO: 32) Hamp1-R −ATAAATAAGGACGGGAGGGG (SEQ ID NO: 33)

To generate cDNA encoding HJV.Fc, an upstream fragment of humanhemojuvelin (containing a preprotrypsin signal sequence and FLAG tag)was digested SpeI/BstEII from the plasmid FLAG-HJV (Babitt et al., 2006.Nat. Genet. 38:531-539). A downstream fragment of human hemojuvelin thatdoes not include the glycophosphatidylinositol (GPI) domain wasamplified by PCR from the plasmid FLAG-HJV using the primers5′-AGAAGGTGTATCAGGCTGAGGTGG-3′ (SEQ ID NO: 34) and5′-CAGCTCGAGTGAGGGGAAGAGATGCAGCTTCTC-3′ (SEQ ID NO: 35), followed byBstEII/XhoI digestion. Both fragments were ligated into the SpeI/XhoIsites of Signal PigPlus (R & D Systems) in-frame with Fc portion ofhuman IgG. Sequences were verified by bi-directional sequencing at theDNA sequencing core facility of Massachusetts General Hospital.

Purification of HJV.Fc.

Two methods were used. CHO cells stably expressing Hjv.Fc were culturedin F-12K NutrientMixture, Kaighn's Modification, supplemented with 5%ultra-low immunoglobulin FBS (Invitrogen) using 175-cm2 multifloorflasks (Denville Scientific). Hjv.Fc was purified from the medium ofstably transfected cells via one-step Protein A affinity chromatographyusing HiTrap rProtein A FF columns (Amersham Biosciences) as describedin Babitt et al., J. Biol. Chem. 280, 29820-29827 (2005) and del Re etal., J. Biol. Chem. 279, 22765-22772 (2004). Hjv.Fc was subjected toreducing SDS-PAGE and gels were stained with Bio-safe Coomassie blue(Bio-Rad) to determine purity and quantify protein concentration.

Alternatively, HEK293 cells (ATCC #CRL-1573) cultured in RPMI medium1640 (GIBCO) supplemented with L-glutamine (GIBCO) and 10% FBS (AtlantaBiologicals) were stably transfected with cDNA encoding HJV.Fc usingLipofectamine 2000 (Invitrogen) according to manufacturer instructions.Stably transfected cells were selected and cultured in 1 mg/ml Geneticin(Cellgro Mediatech). HJV.Fc was purified from the conditioned media ofstably transfected cells by Bioexpress.

Generation of Antibody to Hemojuvelin (α-HJV) and Protein Blot Analysis.

An affinity-purified rabbit polyclonal antibody to hemojuvelin (α-HJV)was raised against the peptide 292-RVAEDVARAFSAEQDLQLC-310 (SEQ ID NO:36) in the C terminus of mouse hemojuvelin upstream of its hydrophobictail (Papanikolaou et al., Nat. Genet. 36, 77-82 (2004); Samad et al.,J. Neurosci. 24, 2027-2036 (2004)). Livers from 12956/SvEvTac wild-typeor Hfe2^(−/−) mice 19, or cells transfected with cDNA encoding wild-typeor mutant hemojuvelin, were homogenized and sonicated in lysis buffer(200 mM Tris-HCl, pH 8, 100 mM NaCl, 1 mM EDTA, 0.5% NP-40 and 10%glycerol) containing a mixture of protease inhibitors (Roche) asdescribed in Babitt et al., J. Biol. Chem. 280, 29820-29827 (2005). Forassays examining phosphorylated Smad expression, 1 mM sodiumorthovanadate (Sigma) and 1 mM sodium fluoride (Sigma) were added to thelysis buffer as phosphatase inhibitors. Purified Hjv.Fc, transfectedcell lysates or liver lysates, were subjected to reducing SDS-PAGE andprotein blot using (i) α-HJV (1:1,000, 4 mg ml⁻¹) at 4° C. overnight,(ii) goat anti-human Fc antibody (1:1,000; Jackson ImmunoResearchLaboratories) at 23° C. for 1 h or (iii) rabbit polyclonal antibody tophosphorylated Smad1/5/8 (1:1,000; Cell Signaling) at 4° C. overnight(Babitt et al., J. Biol. Chem. 280, 29820-29827 (2005)). Blots werestripped and reprobed with mouse monoclonal antibody to β-actin(1:5,000; Sigma), rabbit polyclonal antibody to Smad1 (1:250; UpstateBiotechnology) at 4° C. overnight, or rabbit polyclonal antibody toactin (1:50; Biomedical Technologies) at room temperature for 1 h asloading controls.

Ligand Iodination and Crosslinking.

The inventors iodinated 2 mg of carrier-free human BMP-2 or BMP-4 ligand(R & D Systems) per reaction with ¹²⁵I by the modifiedchloramine-Tmethod as previously described (Frolik et al., J. Biol.Chem. 259, 10995-11000 ((1984)). ¹²⁵I-BMP-2 was incubated with 60 ngHjv.Fc for ALK5.Fc (R & D Systems) in 20 mM HEPES (pH 7.8) with 0.1% BSAand a mixture of protease inhibitors (Roche Diagnostics) or with bufferalone. This mixture was incubated in the absence or presence of 2.5 MDSS (Sigma) followed by incubation with Protein A Sepharose beads(Amersham) as described in Babitt et al., J. Biol. Chem. 280,29820-29827 (2005). Beads were washed with PBS and protein was eluted bynonreducing Laemmli sample buffer (Bio-Rad). Eluted protein wasseparated by SDS-PAGE and analyzed by autoradiography.

Hepcidin Induction Assays, Quantitative Real-Time PCR and RT-PCR.

HepG2 or Hep3B cells were grown to 60% confluence on 6-cm tissue cultureplates. Where indicated, cells were transfected with varying amounts ofcDNA encoding Flag-HJV or Flag-G99V-HJV. Cells were serum-starved 24 hafter transfection in α-MEM with 1% FBS followed by incubation with 50ng ml⁻¹ BMP-2 at 37° C. for various times or with 1 mg ml⁻¹ noggin at 371 C for 48 h. For cycloheximide experiments, 10 mg ml⁻¹ cycloheximidewas added for 30 min before addition of BMP-2. Total RNA was isolatedusing the RNeasy Mini Kit (QIAgen), with DNAse digestion by theRNase-Free DNase Set (QIAgen) according to the manufacturer'sinstructions. Real-time quantification of mRNA transcripts was performedusing two-step RT-PCR using the ABI Prism 7900HT Sequence DetectionSystem and SDS software version 2.0. Firststrand cDNA synthesis wasperformed using iScript cDNA Synthesis Kit (Bio-Rad) according to themanufacturer's instructions, using 2 mg total RNA template per sample.In a second step, hepcidin (HAMP) transcripts were amplified with theprimers HAMP-F and HAMP-R and detected using iTaq SYBR Green Supermixwith ROX (Biorad) according to the manufacturer's instructions. Inparallel, β-actin (ACTB) transcripts were amplified with the primersACTB-F and ACTB-R and detected in a similar manner to serve as aninternal control. Standard curves for hepcidin and β-actin weregenerated from accurately determined dilutions of plasmids containingcDNA encoding hepcidin and β-actin as templates. Samples were analyzedin triplicate, and results are reported as the ratio of mean values forhepcidin to β-actin. BMP2 and BMP4 transcripts were amplified from HepG2cDNA generated above using the primers BMP2-F and BMP2-R (for BMP2) andBMP4-F and BMP4-R (for BMP4) (see Table 1 for primer sequences).

Animals.

Six to eight week old 12956/SvEvTac mice (Taconic) were fed on eitherthe Prolab 5P75 Isopro RMH 3000 or Prolab RMH 3000 diet, each with 380parts per million iron.

BMP Injection.

Mice were anesthetized with Avertin (Sigma) and given a singleretro-orbital injection of 1 mg/kg of BMP-2 (kindly provided by Dr.Vicki Rosen, Harvard School of Dental Medicine, Boston, Mass.) in 0.1%BSA in 1×PBS or an equal volume of vehicle alone. Dosage of BMP-2 wasbased on published data for BMP-7 showing that doses ranging from0.25-1.0 mg/kg IV or IP are effective in inhibiting fibrosis andpreserving renal function in several animal models of kidney injury(Matsunaga et al., Nat. Cell Biol. 6, 749-755 (2004); Courselaud et al.,J. Biol. Chem. 277, 41163-41170 (2002); del Re et al., J. Biol. Chem.279, 22765-22772 (2004); Frolik et al., J. Biol. Chem. 259, 10995-11000(1984); Lin et al., Cell 119, 121-135 (2004)). Four hours afterinjection the mice were sacrificed, and blood and livers were harvestedfor measurement of iron parameters and hepcidin expression.

HJV.Fc Injection.

Mice were injected with an intraperitoneal dose of 25 mg/kg purifiedHJV.Fc or an equal volume of normal saline three times per week forthree weeks. Twenty-four hours after the last injection, mice weresacrificed and blood, livers, and spleen were harvested for measurementof iron parameters, phosphorylated Smad1/5/8, and hepcidin expression.

Serum Iron Measurements.

Blood was collected in BD Microtainer serum separator tubes (FisherScientific) and serum was isolated according to the manufacturer'sinstructions. Serum iron and unsaturated iron-binding capacity (UIBC)were measured by colorimetric assay using the Iron/UIBC kit (ThermoElectron Corporation). Total iron binding capacity (TIBC) was calculatedas the sum of serum iron and UIBC measurements, and transferrinsaturation percentage was calculated as serum iron/TIBC×100.

Tissue Iron Measurement.

Immediately after harvest, livers and spleen were sectioned and weighed.Quantitative measurement of non-heme iron was measured according to themethod of Torrence and Bothwell (Alonso et al., J. Mol. Evol. 23, 11-22(1986)). Results are reported as μg iron/gram wet weight tissue.

Luciferase Assay.

Hepcidin promoter luciferase assays in hepatoma-derived Hep3B cells werecarried out using the Dual-Luciferase system (Promega) as described inBabitt et al., 2006. Nat. Genet. 38:531-539 with the followingmodifications. For BMP/TGF-β-stimulation assays, cells transfected withthe hepcidin promoter luciferase reporter and control Renilla luciferasevector (pRL-TK) were serum starved in α-MEM with L-glutamine(Invitrogen) supplemented with 1% FBS for 6 hours, followed bystimulation with 50 ng/ml BMP ligands, 30 ng/ml Activin A, or 5 ng/mlTGF-β ligands (R & D Systems), for 16 hours. Relative concentrations ofBMP/TGF-β superfamily ligands are similar to those previously used byothers to compare superfamily ligand responses (Wang et al., 2005. CellMetab. 2:399-409, Korchynskyi et al., 2002. J. Biol. Chem.277:4883-4891; Dennler et al., 1998. EMBO J. 17:3091-3100). For HJV.Fcinhibition assays, cells transfected with the hepcidin promoterluciferase reporter and pRL-TK were serum starved as above and incubatedwith 25 ng/ml BMP-2, -4, -6, -7 ligands, 50 ng/ml BMP-5, or 5 ng/mlBMP-9, either alone or with 0.5-25 μg/ml of HJV.Fc for 16 hours.Relative concentrations of BMP ligands were chosen to elicit similardegrees of hepcidin promoter relative luciferase activity. Experimentsusing equal concentrations of ligands were also carried out and hadsimilar results (data not shown).

Primary Hepatocyte Isolation and Culture.

Primary hepatocytes were isolated by collagenase digestion of liversfrom 8- to 10-week-old 12956/SvEvTac wildtype or Hfe2^(−/−) mice usingmethods described in Lin et al., Cell 119, 121-135 (2004). Briefly, micewere perfused through the inferior vena cava with calcium-free Hank'sBalanced Salt Solution (HBSS; Mediatech) supplemented with 0.5 mM EDTAand 16.7 mM sodium bicarbonate for 4 min at a rate of B1.5 ml min⁻¹.Mice were subsequently perfused with calcium-containing HBSS containing0.05% collagenase (Sigma), 1% bovine serum albumin and 16.7 mM sodiumbicarbonate for 8 min. After enzymatic digestion, hepatocytes wereliberated into culture medium (1:1 Dulbecco's Modified Eagle's/Ham's F12medium (Gibco) supplemented with 100 IU ml⁻¹ penicillin, 100 mg ml⁻¹streptomycin, 18 mM HEPES, 1 mM sodium pyruvate, 10 mg ml⁻¹ insulin, 5.5mg ml⁻¹ transferrin, 5 ng ml⁻¹ selenium (ITS; Sigma), 2 mM L-glutamine,0.1 mM non-essential amino acids (Gibco) and 10% FBS (HyClone)), passedthrough a 100-mm BD Falcon mesh cell strainer (BD Biosciences),centrifuged, gently washed with culture medium and counted. Cells (490%hepatocytes by microscopy) were seeded on collagen-coated plates (Sigma)at 5×10⁵ cells per 60-mm dish. After 2 to 3 h, cells were washed withPBS, serum-starved with culture medium containing 1% FBS for 6 h andstimulated with recombinant human BMP-2 at varying concentrations for 12h. RNA was isolated using the RNeasy kit according to manufacturer'sdirections (QIAgen).

RNA Blot Analysis.

Total RNA (2.5 mg) from primary hepatocytes was separated on a 1%formaldehyde agarose gel and transferred onto Hybond N+ membranes(Amersham Pharmacia Biotech). Membranes were baked for 2 h at 80 1 Cunder vacuum and hybridized with radioactively labeled probes specificfor mouse hepcidin 1 (Hamp1, amplified with primers Hamp1-F and Hamp1-R(see table 1 for primer sequences) and for β-actin. Expression wasquantified using a phosphorimager (Molecular Dynamics/AmershamBiosciences) and normalized to β-actin or 28S rRNA as loading controls.See Table 1 for primer sequences.

RT-PCR.

Total RNA was isolated from HepG2 or Hep3B cells and was analyzed forBMP2, BMP4, BMP5, BMP6, and BMP9 expression as previously described (29)using the primers BMP2-F, BMP2-R, BMP4-F, BMP4-R, BMP6-F, BMP6-R,BMP9-F, and BMP9-R (see Table 1 for primer sequences).

Quantitative Real-Time RT-PCR.

Hep3B or HepG2 cells were serum starved for 6 hours in α-MEMsupplemented with 1% FBS and treated for 16 hours with varying amountsof BMP/TGF-β superfamily ligands or 100 ng/ml IL-6, in the absence orpresence of 25 μg/ml purified HJV.Fc. For BMP siRNA experiments, HepG2cells were plated in 24-well plates and transfected with 200 ng pcDNA3(Invitrogen) and 40 nM BMP-2, BMP-4, BMP-6, BMP-7, or Control scramblesiRNA (Ambion, see Table 2 for siRNA sequences) in α-MEM usingLipofectamine 2000® (Invitrogen) according to the manufacturer'sinstructions. Cells were serum starved overnight in α-MEM supplementedwith 0.1% BSA. Total RNA was isolated from treated cells, and real-timequantitation of hepcidin relative to β-actin mRNA transcripts wasperformed using 2-step quantitative real-time RT-PCR as previouslydescribed (Babitt et al., 2006. Nat. Genet. 38:531-539). For BMP siRNAexperiments, real-time quantitation of BMP2, BMP4, and BMP6 relative toβ-actin mRNA transcripts was also performed as described above using theprimers qBMP2-F, qBMP2-R, qBMP4-F, qBMP4-R, qBMP6-F, qBMP6-R (see Table1 for primer sequences). For mouse livers, total RNA was isolated usingthe Illustra RNAspin Mini Kit (GE Healthcare) according to themanufacturer's instructions. Real-time quantification of hepcidin(Hamp1) relative to Gapdh mRNA transcripts was performed as describedabove using primers Hamp1-F (6) Hamp1-R (6), Gapdh-F, and Gapdh-R.

TABLE 2 Sequence of siRNAs for BMP ligands (Ambion) NameSequence (sense) BMP2 GGUUUUCCGAGAACAGAUGtt (SEQ ID NO: 65) BMP4GGGACCAGUGAAAACUCUGtt (SEQ ID NO: 67) BMP6GCGACACCACAAAGAGUUCtt (SEQ ID NO: 68) BMP7GGCAAAACCUAGCAGGAAAtt (SEQ ID NO: 69)

Western Blot.

Western blot of purified HJV.Fc using anti-hemojuvelin antibody (Babittet al., 2006. Nat. Genet. 38:531-539) and anti-Fc antibody (JacksonImmunoResearch Laboratories) was performed as described in Babitt etal., 2006. Nat. Genet. 38:531-539. Western blot of liver lysates forphosphorylated Smad1/5/8 expression relative to total Smad1 and β-actinexpression was performed as described in Babitt et al., 2006. Nat.Genet. 38:531-539. For ferroportin assays, spleen membrane preparationswere prepared as previously described (Canonne-Hergaux et al., 1999.Blood. 93:4406-4417). Protein concentrations were determined by BCAassay (Pierce). After solubilization in 1× Laemmli buffer for 30 minutesat room temperature, 35 μg of protein per sample were separated bySDSPAGE using pre-cast NuPAGE Novex 4-12% Bis-Tris gels (Invitrogen) andtransferred onto PDVF membranes. Western blot for was performed usinganti-ferroportin antibody (kindly donated by Francois Canonne-Hergaux)as previously described (Canonne-Hergaux et al., 2005. Am. J. Physiol.Gastrointest. Liver Physiol. 290:156-163). Blots were stripped andreprobed for β-actin expression as a loading control as described inBabitt et al., 2006. Nat. Genet. 38:531-539 and herein.

Cell Culture and Transfection.

CHO cells (ATCC) were cultured in F-12K Nutrient Mixture, Kaighn'sModification (Invitrogen) supplemented with 10% fetal bovine serum (FBS;Atlanta Biologicals). HepG2 cells and Hep3B cells (ATCC) were culturedin Minimal Essential Alpha Medium with L-glutamine (α-MEM, Invitrogen)containing 10% FBS. HEK293 cells (ATCC) were cultured in DMEM (CellgroMediatech) supplemented with 10% FBS. All plasmid transfections wereperformed with Lipofectamine 2000 (Invitrogen) or Effectene transfectionreagent (QIAgen) according to manufacturer instructions. Stablytransfected cells were selected and cultured in 1 mg ml-1 geneticin(Cellgro Mediatech).

Luciferase Assay.

HepG2 or Hep3B cells were transiently transfected with 2.5 mg BMPresponsive luciferase reporter (BRE-Luc), 2.5 mg TGF-β responsiveluciferase reporter, (CAGA)12 MPL-Luc (CAGA-Luc) (both provided by P.ten Dijke, Leiden University Medical Center, The Netherlands) or 2.5 mghepcidin promoter luciferase reporter construct, in combination with0.25 mg pRL-TK Renilla luciferase vector (Promega) to control fortransfection efficiency, with or without cotransfection with cDNAencoding wild-type or mutant hemojuvelin. Cells were serum-starved 48 hafter transfection in α-MEM supplemented with 1% FBS for 6 h and treatedwith 1 ng ml⁻¹ TGF-β1 or 25-50 ng ml-1 BMP ligands (R & D Systems) for16 h, in the absence or presence of 1 mg ml-1 noggin (R & D Systems) or20 mg ml-1 neutralizing antibody to BMP-2 or BMP-4 (R & D Systems).Cells were lysed and luciferase activity was determined with the PromegaDual Reporter Assay according to the manufacturer's instructions.Experiments were performed in duplicate or triplicate wells. Relativeluciferase activity was calculated as the ratio of firefly (reporter) toRenilla (transfection control) luciferase activity and is expressed as amultiple of the activity of unstimulated cells transfected with reporteralone.

Binding Assay.

60 ng purified Hjv.Fc in Tris buffered saline/Casein blocking buffer(BioFX, Owings Mills, Md.) or buffer alone was incubated with ¹²⁵I-BMP-2or ¹²⁵I-BMP-4 at 4° C., either alone or in the presence of 80 ng coldBMP-2, BMP-4, BMP-7 or TGF-β1 (R&D Systems) as described in Babitt etal. J. Biol. Chem. 280, 29820-29827, 2005. The reaction mix was thenincubated for 1.5 hrs at 4° C. on a protein A coated plates (Pierce),plates were washed with wash solution (KPL, Gaithersberg, Md.), andindividual wells were counted with a standard gamma counter.

Crosslinking at the Cell Surface.

HEK293 cells in 10 cm dishes were transfected with 1.5 μg cDNA encodingHA-tagged ALK6 (ALK6-HA, kindly provided by Hideyuki Beppu and KennethBloch, Massachusetts General Hospital, Boston, Mass.), FLAG-tagged humanHJV (FLAG-HJV), or both. Forty-eight hours after transfection, cellswere serum starved for 3 hours in 1% FBS at 37° C. and incubated for 3hours at 4° C. in the absence or presence of 300 ng/ml BMP-2. Cells weredetached in 200 μl cold PBS and incubated with 15 μl of 100 mM DSS inDMSO for 30 minutes at room temperature. After quenching of DSS, cellswere lysed in 10 mM Tris-HCl, pH 7.4, 150 mM NaCl, 1% Triton-100, 2%Octyl-β-Glucoside (Pierce) and a mixture of protease inhibitors (RocheDiagnostics). 380 μl cell lysates were immunoprecipitated with 1 μgrabbit polyclonal anti-HA antibody (#-HA, Santa Cruz, SC-805) at 4° C.overnight followed by incubation with Protein A beads (Pierce) for 6hours at 4° C. Immunoprecipitates were analyzed by reducing SDS-PAGE andWestern blot with mouse monoclonal M5 anti-FLAG antibody (#-FLAG, 1:500dilution, Sigma). Total cell lysates were analyzed by reducing SDSPAGEand Western blot with #-FLAG (1:500) or #-HA (1:1000).

Statistical Analysis.

A two-tailed Student's t-test with P<0.05 was used to determinestatistical significance.

Accession Codes.

GenBank: Homo sapiens hemojuvelin (HEF2) transcript variant a,NM_(—)213653 (SEQ ID NO: 37); Homo sapiens hemojuvelin (HEF2) transcriptvariant b, NM_(—)145277 (SEQ ID NO: 38); BC085604 (SEQ ID NO: 39); Musmusculus hemojuvelin (RgmC) mRNA, AJ557515 (SEQ ID NO: 40); Homo sapiensHAMP mRNA, NM_(—)021175 (SEQ ID NO: 41), BC020612 (SEQ ID NO: 42); Musmusculus hamp1 mRNA, NM_(—)032541 (SEQ ID NO: 43), EST W12193 (SEQ IDNO: 44); Homo sapiens BMP2 mRNA, NM_(—)001200 (SEQ ID NO: 45), BC069214(SEQ ID NO: 46); Homo sapiens BMP4 mRNA, NM_(—)001202 (SEQ ID NO: 47),BC020546 (SEQ ID NO: 48); Homo sapiens ACTB mRNA, NM_(—)001101 (SEQ IDNO: 49), BC001301 (SEQ ID NO: 50).

X. Examples Example 1 Hemojuvelin is a BMP Coreceptor

To test whether hemojuvelin mediates BMP signaling in liver cells,hepatoma-derived HepG2 cells were transfected with a BMP-responsiveluciferase reporter (BRE-Luc) (Korchynskyi et al., J. Biol. Chem. 277,4883-4891 (2002)), either alone or in combination with cDNA encodingmouse hemojuvelin (Hjv). Transfected cells were incubated with orwithout BMP-2 and measured luciferase activity. Stimulation withexogenous BMP-2 increased BRE luciferase activity B18-fold over baseline(FIGS. 2A and 2B). Hjv increased BRE luciferase activity in adose-dependent fashion, even in the absence of exogenous BMP-2 (FIG.2A). In contrast, Hjv did not increase TGF-β-responsive CAGA luciferaseactivity (FIG. 2B) (Dennler et al., EMBO J. 17, 3091-3100 (1998)). Theinventors obtained similar results in another hepatoma-derived cellline, Hep3B cells (data not shown). Thus, hemojuvelin enhances BMP, butnot TGF-β, signaling.

Hemojuvelin's ability to generate BMP signals without exogenous BMPligand raises the question of whether hemojuvelin enhances signaling byendogenous BMP ligands, or whether it acts in a ligand-independentmanner. The inventors therefore determined whether hemojuvelin-mediatedBMP signaling was inhibited by noggin, a soluble BMP inhibitor thatbinds to BMP ligands and blocks the binding epitopes for BMP receptors(Balemans et al., Dev. Biol. 250, 231-250 (2002); Groppe et al., Nature420, 636-642 (2002)). In a manner similar to its effects on exogenousBMP-2, noggin protein inhibited BRE luciferase stimulation by Hjv,suggesting that hemojuvelin-mediated signaling requires BMP ligands(FIGS. 3A-3C). Similar results were obtained using a neutralizingantibody against BMP-2 and BMP-4 (aBMP2/4) in place of noggin,suggesting that hemojuvelin, like family members RGMA and DRAGON, mayhave ligand selectivity for BMP-2, BMP-4 or both (FIGS. 3A-3C).Expression of both endogenous BMP2 and BMP4 mRNA by RT-PCR in thesecells was detected (FIGS. 3A-3C).

The inventors then investigated whether hemojuvelin interacts directlywith BMP-2 and/or BMP-4 ligands. The inventors generated solublehemojuvelin fusion protein (Hjv.Fc) by fusing the extracellular domainof mouse Hjv to the Fc portion of human immunoglobulin G (FIGS. 4A-4C).The inventors incubated purified Hjv.Fc overnight with ¹²⁵I-labeledBMP-2 (¹²⁵I-BMP-2) or ¹²⁵I-labeled BMP-4 (¹²⁵I-BMP-4) in the absence orpresence of excess unlabeled BMP-2, BMP-4, BMP-7 or TGF-β1, transferredit to Protein A-coated plates and measured bound radioactivity. Hjv.Fcbound to ¹²⁵I-BMP-2 and ¹²⁵I-BMP-4, and this binding was competitivelyinhibited by excess unlabeled BMP-2 and, to a lesser extent, by BMP-4,but not by BMP-7 or TGF-131 (FIGS. 4A-4C). As further confirmation of aninteraction between hemojuvelin and BMP-2, ¹²⁵I-BMP-2 was chemicallycrosslinked with Hjv.Fc in the presence of disuccinimidyl suberate (DSS;FIG. 5), and this crosslinking was inhibited by excess unlabeled BMP-2(FIG. 5). No bands were observed when the inventors used buffer alone orALK5.Fc (a TGF-β type I receptor) in place of Hjv.Fc or if DSS wasabsent (FIG. 5). These data collectively suggest that Hjv.Fc binds toradiolabeled BMP-2 and, to a lesser extent, BMP-4. To examine whetherhemojuvelin-mediated BMP signaling requires BMP receptors, the inventorstested the effects of dominant-negative mutant BMP type I receptors ALK3and ALK6 in our reporter assay system. These dominant-negative mutantsare deficient in kinase activity and therefore unable to phosphorylateSmad proteins (Samad et al., J. Biol. Chem. 280, 14122-14129 (2005);Babitt et al., J. Biol. Chem. 280, 29820-29827 (2005); Clarke et al.,Mol. Endocrinol. 15, 946-959 (2001)). BRE luciferase activity induced bytransfection with Hjv or incubation of cells with exogenous BMP-2 wasinhibited by coexpression with dominant-negative ALK3 or ALK6 (FIGS. 6Aand 6B). Thus, hemojuvelin-mediated BMP signaling involves BMP type Ireceptors.

The inventors then determined whether hemojuvelin interacts directlywith BMP type I receptors at the cell surface and whether thisinteraction depends on the presence of BMP ligands using acoimmunoprecipitation assay in HEK293 cells, a human embryonic kidneycell line with high recombinant protein expression. The inventorsgenerated Flag-tagged human hemojuvelin (Flag-HJV) and coexpressed it inHEK293 cells with hemagglutinin-tagged ALK6 (ALK6-HA), in the absence orpresence of exogenous BMP-2 ligand, followed by crosslinking with DSSand immunoprecipitation with antibody to hemagglutinin. Protein blot ofimmunoprecipitates with antibody to Flag demonstrated that Flag-HJVformed a complex with ALK6-HA in the presence of BMP-2 (FIGS. 6A and6B).

Next, the inventors tested whether hemojuvelin mediates BMP signalingvia the classical BMP signaling pathway involving BMP receptor-activatedSmad1 using our luciferase assay system. Coexpression of wild-type Smad1and Hjv further augmented the BRE luciferase activity induced by Hjvalone, whereas coexpression of dominant-negative Smad1 (with deletedphosphoacceptor residues 24, 25, 35, 36) and Hjv blocked the BREluciferase activity induced by Hjv alone (FIG. 7) (Samad et al., J.Biol. Chem. 280, 14122-14129 (2005); Babitt et al., J. Biol. Chem. 280,29820-29827 (2005); Macias-Silva et al., J. Biol. Chem. 273, 25628-25636(1998); Piscione et al., Am. J. Physiol. Renal Physiol. 280, F19-F33(2001)). Wild-type and dominant-negative Smad1 had similar effects onexogenous BMP-2 stimulation (FIG. 7). Thus, hemojuvelin mediates BMPsignaling via the classical BMP signaling pathway that involves BMPreceptor-activated Smad1.

Example 2 Hemojuvelin Mutants have Impaired BMP Signaling Ability

A common mutation in HFE2 that results in juvenile hemochromatosis is apoint mutation substituting valine for glycine at amino acid 320(corresponding to amino acid 313 in mouse hemojuvelin) (Papanikolaou etal., Nat. Genet. 36, 77-82 (2004); Lanzara et al., Blood 103, 4317-4321(2004); Lee et al., Blood 103, 4669-4671 (2004)). The inventorsgenerated cDNA encoding the equivalent mouse mutation, G313V-Hjv, andinvestigated whether this mutant had an altered ability to mediate BMPsignaling. Using CHO cells, which lack native hemojuvelin andefficiently express transfected proteins, the inventors firstdemonstrated that G313V-Hjv was expressed by protein blot using anantibody to hemojuvelin (α-HJV, FIG. 8A). G313V-Hjv migrated with adifferent pattern than wild-type Hjv, suggesting that it may beprocessed differently, at least in this cell type (FIG. 8A). Theinventors then examined the ability of G313V-Hjv versus wild-type Hjv toenhance endogenous BMP signaling in HepG2 cells. Hjv increased BREluciferase activity in a dose-dependent fashion up to 23-fold (FIG. 8B).In contrast, G313V-Hjv was able to stimulate BRE luciferase activity toa maximum of only eightfold (FIG. 8B). The inventors found similarresults in Hep3B cells (data not shown).

Although Hjv and G313V-Hjv were expressed at approximately equivalentlevels in CHO cells, the inventors could not detect expression of theseproteins by protein blot in HepG2 or Hep3B cells, presumably owing tolow expression efficiency or the sensitivity of our antibody. Theinventors therefore generated cDNA encoding Flag-tagged humanhemojuvelin (Flag-HJV), replacing the signal peptide of nativehemojuvelin with that from preprotrypsin and adding a Flag tag to theN-terminus. The inventors also used this construct to generate cDNAencoding Flag-G99V-HJV, containing a valine-for-glycine substitution atamino acid 99, another hemojuvelin mutation associated with juvenilehemochromatosis Like wild-type mouse hemojuvelin (Hjv), Flag-HJV wasable to stimulate BRE luciferase activity (FIG. 8C) in Hep3B cells. Incontrast, mutant Flag-G99V-HJV had a significantly reduced ability tostimulate BRE luciferase activity compared with Flag-HJV (FIG. 8C). Theinventors saw similar results in HepG2 cells (data not shown). Proteinblot using α-HJV (FIG. 8D) and antibody to Flag (data not shown) showedthat Flag-HJV and Flag-G99V-HJV had similar expression levels in Hep3Bcells.

Hfe2^(−/−) mice mirror the iron overload phenotype seen in juvenilehemochromatosis (Huang et al., J. Clin. Invest. 115, 2187-2191 (2005)).To further support a physiologic role for hemojuvelin in BMP signalingin liver cells in vivo, the inventors assayed liver lysates fromwild-type and Hfe2^(−/−) mice for phosphorylated Smad1, Smad5 and Smad8(Smad1/5/8) by protein blot as an indicator of basal BMP signaling. Theinventors quantified chemiluminescence and normalized results to totalSmad1 and β-actin as loading controls. Hfe2^(−/−) livers hadsignificantly lower levels of basal phosphorylated Smad1/5/8 thanwild-type livers (FIG. 9).

Collectively, these findings demonstrate that mutations in hemojuvelin,the equivalent of which in humans cause juvenile hemochromatosis, resultin decreased BMP signaling in liver cells. Furthermore, the absence ofhemojuvelin in Hfe2^(−/−) mouse livers results in reduced BMP signaling.This raises the possibility of a link between hemojuvelin's BMPsignaling ability and its role in iron metabolism.

Example 3 Hemojuvelin Increases Hepcidin Expression in Liver Cells

It has been hypothesized that hemojuvelin positively regulates hepcidinexpression and that iron overload in individuals with HFE2 mutations isdue to reduced hepcidin levels and consequent ferroportin overexpression(Papanikolaou et al., Nat. Genet. 36, 77-82 (2004), Huang et al., J.Clin. Invest. 115, 2187-2191 (2005); Niederkofler et al., J. Clin.Invest. 115, 2180-2186 (2005); Lin et al., Blood 106, 2884-2889(2005)19-21). The inventors therefore used quantitative real-time PCR todirectly test whether transfection of cDNA encoding hemojuvelin intoliver cells upregulates hepcidin mRNA expression and whether hemojuvelinmutants have an altered ability to upregulate hepcidin expression.Flag-HJV significantly increased hepcidin mRNA expression in adose-dependent fashion in Hep3B cells (FIG. 10A). By contrast, mutantFlag-G99V-HJV had an impaired ability to increase the hepcidinexpression compared with Flag-HJV (FIG. 10B).

As the sensitivity of this assay is limited by transfection efficiency,the inventors also examined the relative ability of wild-type Hjv orFlag-HJV versus mutant G313V-Hjv or Flag-G99V-HJV to activate thehepcidin promoter using a dual luciferase assay. The inventorstransfected Hep3B cells with a hepcidin promoter/firefly luciferaseconstruct and a Renilla luciferase vector. The inventors calculatedrelative luciferase activity as the ratio of firefly luciferase activityto Renilla luciferase activity, to control for transfection efficiency.Coexpression with Flag-HJV (FIG. 10C) or Hjv (FIG. 10D) significantlyincreased hepcidin promoter relative luciferase activity compared withcells not transfected with hemojuvelin, consistent with the findings byreal-time PCR. Furthermore, mutant Flag-G99V-HJV (FIG. 10C) andG313V-Hjv (FIG. 10D) had a significantly impaired ability to activatehepcidin promoter luciferase activity compared with Flag-HJV and Hjv.

Example 4 BMP-2 Increases Hepcidin Expression in Liver Cells

The inventors then investigated whether hemojuvelin's BMP signalingability might be the mechanism by which hemojuvelin regulates hepcidinexpression in liver cells. The inventors performed quantitativereal-time PCR to test for hepcidin mRNA expression in HepG2 (FIG. 11A)or Hep3B cells (FIG. 11B) after no treatment, stimulation with exogenousBMP-2 or incubation with exogenous noggin. Exogenous BMP-2 significantlyincreased the hepcidin/β-actin mRNA ratio by 12-fold in HepG2 cells(FIG. 11A) and by 260-fold in Hep3B cells (FIG. 11B). Thehepcidin/β-actin ratio began to increase 0.5 to 1 h after addition ofexogenous BMP-2 (FIG. 11C). In contrast, inhibition of endogenous BMPsignaling with noggin significantly decreased the hepcidin/β-actin ratio12-fold below baseline in HepG2 cells (FIG. 11A), although the inventorsdid not see any inhibition in Hep3B cells (FIG. 11B), in which basalhepcidin mRNA levels were much lower (data not shown). These changeswere predominantly due to alterations in hepcidin mRNA levels, as bactinmRNA expression varied up to only 1.6-fold over all experiments (datanot shown). Thus, BMP-2 positively regulates hepcidin expression inliver cells.

Examination of the hepcidin promoter demonstrated several potential BMPresponsive elements (FIG. 12), suggesting that hemojuvelin mightregulate hepcidin expression directly at the transcriptional level. Theinventors therefore tested the ability of cycloheximide, an inhibitor ofde novo protein synthesis, to inhibit BMP-2 induction of hepcidin mRNAexpression using quantitative real-time PCR, and the inventors testedthe ability of BMP-2 to activate the hepcidin promoter using thehepcidin promoter luciferase construct. Cycloheximide had no effect onBMP-2 induction of hepcidin expression (FIG. 13), suggesting that denovo protein synthesis is not required for BMP-2 regulation of hepcidinlevels. Exogenous BMP-2 increased hepcidin promoter luciferase activityin a dose-dependent fashion up to 100-fold, suggesting that BMP-2increases transcription of hepcidin mRNA (FIG. 11D). The inventors sawsimilar results in HepG2 cells, although the degree of stimulation waslower (data not shown). Thus, BMP-2 directly upregulates transcriptionof hepcidin mRNA.

Example 5 Hepcidin Induction by BMP-2 is Enhanced by Hemojuvelin

As hemojuvelin enhances cellular responses to BMP-2, and BMP-2positively regulates hepcidin expression, the inventors tested whetherhemojuvelin enhances the upregulation of hepcidin expression by BMP-2.Coexpression of the hepcidin promoter luciferase construct with Flag-HJVor Hjv increased hepcidin promoter luciferase activity in response to afixed dose of BMP-2 (FIGS. 14A-14C). In contrast, coexpression of thehepcidin promoter luciferase construct with mutant Flag-G99V-HJV orG313V-Hjv resulted in significantly less activation of the hepcidinpromoter in response to BMP-2 compared with the results of coexpressionwith Flag-HJV or Hjv (FIGS. 14B and 14C).

Next, the inventors tested whether liver cells lacking hemojuvelin hadimpaired induction of hepcidin expression in response to BMP-2. Theinventors incubated primary hepatocyte cultures from wild-type(Hfe2^(+/+)) or Hfe2^(−/−) mice with or without exogenous BMP-2 and thenassayed for hepcidin mRNA by RNA blot. Consistent with our results inHepG2 and Hep3B cells (FIGS. 11A-11D), BMP-2 increased hepcidin mRNAexpression in wild-type primary hepatocytes. In contrast, although BMP-2was able to increase hepcidin mRNA expression to some extent inHfe2^(−/−) hepatocytes, the response was significantly blunted comparedwith wild-type hepatocytes (FIG. 14D). Hemojuvelin therefore enhanceshepcidin induction in response to BMP-2, although hemojuvelin does notseem absolutely necessary to generate cellular responses to BMP-2.

Example 6 Selective Regulation of Hepcidin by BMP/TGF-β SuperfamilyMembers

TGF-β superfamily members were tested for their ability to regulatehepcidin using both a hepcidin promoter reporter assay (FIG. 15A) andquantitative real-time RT-PCR (FIG. 15B) in Hep3B hepatoma-derivedcells. Relative concentrations of BMP/TGF-β superfamily ligands used aresimilar to those previously used by others to compare responses amongsuperfamily ligands (Wang et al., 2005. Cell Metab. 2:399-409,Korchynskyi et al., 2002. J. Biol. Chem. 277:4883-4891, Dennler et al.,1998. EMBO J. 17:3091-3100). BMP-2, BMP-4, BMP-5, BMP-6, BMP-7, andBMP-9 robustly increased hepcidin promoter luciferase activity20-100-fold over baseline and increased hepcidin mRNA expression by160-1100-fold. In contrast, TGF-β1, -β2, and -β3 increased hepcidinexpression by only 1.5-3-fold over baseline by both methods. BMP-3,BMP-11, GDF-5, GDF-6, and GDF-7 showed no or comparatively smallhepcidin induction by both methods. ActivinA increased hepcidin promoterrelative luciferase activity by 10-fold, but increased hepcidin mRNAexpression by real-time RT-PCR to a comparatively lesser extent relativeto BMP-2, -4, -5, -6, -7 and -9. Biologic activity of all ligands wasverified by luciferase assay using BMP-responsive (BRELuc, Wang et al.,Cell Metab. 2, 399-409 (2005)) and TGF-β/Activin responsive (CAGA-Luc,Korchynskyi et al., J. Biol. Chem. 277, 4883-4891 (2002)) luciferasereporters. Results using both methods correlated well with each other,suggesting that the hepcidin promoter luciferase assay is a goodsurrogate for hepcidin mRNA expression by quantitative real-time RT-PCR.Thus, many TGF-β superfamily members can positively regulate hepcidinexpression in vitro; however, BMP-2, BMP-4, BMP-5, BMP-6, BMP-7, andBMP-9 are much more potent regulators of hepcidin compared with othersuperfamily members, including all three TGF-β ligands.

Example 7 BMP-2 Administration In Vivo Increases Hepcidin Expression andDecreases Serum Iron

Next, the inventors investigated whether BMP-2 regulates hepcidinexpression and iron metabolism in vivo. Purified BMP-2 at 1 mg/kg wasinjected retro-orbitally into mice, followed by determination of serumiron levels and hepatic hepcidin mRNA expression four hours afterinjection. BMP-2 administration increased hepatic hepcidin mRNAexpression 1.8-fold over mice injected with vehicle alone (FIG. 16A, *P=0.02). BMP-2 administration also decreased serum iron levels from 170μg/dl to 114 μg/dl (FIG. 16B, * P=0.02). This is consistent with a rolefor BMP-2 as a positive regulator of hepcidin expression in vivo.

Example 8 Soluble HJV.Fc Selectively Inhibits BMP Signaling In Vitro

Soluble receptors, such as the soluble TNF receptor etanercept, havebeen used to inhibit ligand activity in vitro and in vivo, presumably bybinding to ligands and preventing their interaction with membrane boundreceptors (Moreland et al., 1997. N. Engl. J. Med. 337:141-147).Interestingly, soluble hemojuvelin has been detected in human sera andhas been shown to inhibit hepcidin expression in cultured cells,although the mechanism for this inhibition was not investigated (Lin etal., 2005. Blood. 106:2884-2889). The inventors therefore generatedpurified soluble human hemojuvelin fused to the Fc portion ofimmunoglobulin (HJV.Fc) (FIG. 17A), the murine homologue of which canbind to BMP-2 and BMP-4 ligands. The inventors then investigated whetherHJV.Fc inhibited basal hepcidin expression and BMP induction of hepcidinexpression in vitro. Using hepatoma-derived HepG2 cells, which havehigher basal hepcidin expression, HJV.Fc inhibited basal hepcidin mRNAexpression by 80% (FIG. 17B * P=0.03). These results are consistent withprior reports using soluble hemojuvelin without an Fc fusion (Lin etal., 2005. Blood. 106:2884-2889), suggesting that the Fc domain does notaffect the function of soluble hemojuvelin. HJV.Fc also inhibited BMP-2induction of hepcidin expression (FIG. 17C, P=0.009) and BMP-2 inducedactivation of the hepcidin promoter in a dose-dependent fashion (FIG.17D, blue line). HJV.Fc inhibition of BMP ligands was selective; HJV.Fcinhibited more than 90% of hepcidin promoter activation induced byBMP-2, -4, -5, and -6, but did not inhibit BMP-9 even at lower ligandconcentrations (FIG. 17D). There was a trend toward low-level inhibitionof BMP-7 (FIG. 17D).

BMP-2 and BMP-4 are endogenously expressed in HepG2 cells. To testwhether inhibition of these endogenous BMP ligands was the mechanism bywhich HJV.Fc decreased basal hepcidin expression in HepG2 cells, theinventors sought to determine if other BMP ligands are endogenouslyexpressed in HepG2 using RT-PCR. The inventors then tested whether siRNAinhibition of these endogenously expressed BMP ligands inhibited basalhepcidin expression in a manner similar to HJV.Fc. BMP-2, BMP-4, andBMP-6 were endogenously expressed in HepG2 cells, with BMP-4 being themost abundant (FIG. 18A). BMP-2, BMP-4, and BMP-6 siRNA each selectivelyand significantly reduced endogenous ligand expression in HepG2 cells by65%, 90%, and 55% respectively as measured by real-time RT-PCR (FIG.18B). BMP-2, BMP-4, and BMP-6 siRNA each significantly inhibited basalhepcidin expression in HepG2 cells by approximately 10% (P=0.012), 35%(P=0 0027), and 15% (P=0.0026) respectively as measured by real-timeRT-PCR (FIG. 18C). As a negative control, neither a Control siRNA nor aBMP-7 specific siRNA inhibited basal hepcidin expression. The relativeability of each ligand to inhibit basal hepcidin correlated with therelative mRNA abundance of the ligand and the strength of siRNAinhibition of ligand expression. Endogenous BMP-2, BMP-4, and BMP-6ligands all may therefore contribute to basal hepcidin expression inHepG2 cells. These data are consistent with HJV.Fc inhibiting basalhepcidin expression by inhibiting endogenous BMP signaling, which mayoccur by binding and sequestering endogenously produced BMP ligands andpreventing their interaction with BMP type I and type II receptors.

Example 9 Soluble HJV.Fc Inhibits Hepatic BMP Signaling, InhibitsHepcidin Expression, Increases Ferroportin Expression, MobilizesReticuloendothelial Cell Iron Stores, and Increases Serum Iron In Vivo

To test whether HJV.Fc administration could regulate hepcidin expressionand iron metabolism in vivo, mice were injected with 25 mg/kg purifiedHJV.Fc or an equal volume of normal saline by intraperitoneal injectionthree times weekly for three weeks. Western blot analysis of liverlysates from these mice showed decreased phosphorylated Smad1/5/8expression relative to total Smad1 expression in HJV.Fc treated micecompared with control mice (FIG. 19A, * P=0.0497), demonstrating thatHJV.Fc decreases hepatic BMP signaling in vivo. Quantitative real-timeRT-PCR analysis revealed a 10-fold decrease in hepatic hepcidin mRNAexpression in HJV.Fc treated mice compared with control mice (FIG.19B, * P=0.003). Consistent with the predicted effects of depressedhepcidin levels to increase ferroportin cell-surface expression,increase intestinal iron absorption, and increase release of iron fromreticuloendothelial stores, HJV.Fc treatment increased ferroportinexpression in the spleen compared with control mice as measured byWestern blot (FIG. 19C). HJV.Fc treatment also increased serum ironlevels from 177+/−26 μg/dl to 309+/−2 μg/dl (FIG. 19D, * P=0.01) andincreased serum transferrin saturation from 70% to 100% (FIG. 19E, *P=0.004). Furthermore, HJV.Fc treatment increased hepatic tissue ironcontent by approximately 2-fold (FIG. 19F, * P=0.03) and reduced splenictissue iron content by almost 60% (FIG. 19G, * P=0.009). The inventorsalso determined that mice injected with 5 mg/kg purified HJV.Fc or anequal volume of normal saline by intraperitoneal injection three timesweekly for three weeks demonstrated about a 2-fold increase in serumiron with 5 mg/kg as compared with the saline control (FIG. 22A), andalso increased serum transferrin saturation from about 60% to about 85%(FIG. 22B), demonstrating that administration of soluble HJV iseffective at increasing serum iron concentrations and serum transferrinsaturation in vivo at a wide range of doses, for example from about 0.1mg/kg to about 50 mg/kg, such as from 1 mg/kg to 25 mg/kg or higher.

Example 10 Soluble HJV.Fc Inhibits IL-6 Induction of Hepcidin Expression

Inflammatory cytokines induce hepcidin expression, and this hepcidinexcess is thought to play a role in the anemia of chronic disease (Weisset al., 2005. N. Engl. J. Med. 352:1011-1023; Pigeon et al., 2001. J.Biol. Chem. 276:7811-7819; Nicolas et al., 2002. J. Clin. Invest.110:1037-1044; Nemeth et al., 2004. J. Clin. Invest. 113:1271-1276;Nemeth et al., 2003. Blood. 101:2461-2463; Lee et al., 2005. Proc. Natl.Acad. Sci. USA. 102:1906-1910). The inventors therefore investigatedwhether HJV.Fc could inhibit hepcidin induction by the inflammatorycytokine IL-6. IL-6 increased hepcidin expression 3.3-fold in HepG2cells as measured by real-time RT-PCR (FIG. 20, *P=0.003). Hepcidininduction by IL-6 was significantly abrogated when cells were incubatedwith HJV.Fc in combination with IL-6 (FIG. 20, **P=0.0006 compared withcells treated with IL-6 alone).

REFERENCES

All publications, patents, and patent applications mentioned in thisspecification are incorporated by reference to the same extent as ifeach individual publication or patent was specifically and individuallyindicated to be incorporated by reference.

What is claimed is:
 1. A fusion protein comprising: (a) a hemojuvelin(HJV) polypeptide or fragment thereof, wherein said polypeptide orfragment thereof has at least 95% amino acid sequence identity to aportion of the HJV protein of SEQ ID NOs: 2, 3 or 4 and is at least 50amino acids in length; and (b) a first fusion partner, wherein saidfirst fusion partner is conjugated to said HJV polypeptide or fragmentthereof, wherein said first fusion partner is an IgG1 Fc; and (c) asecond fusion partner.
 2. The fusion protein of claim 1, wherein saidfirst fusion partner is fused to the N-terminus or to the C-terminus ofthe HJV protein fragment.
 3. The fusion protein of claim 1, wherein saidIgG1 Fc is human IgG1 Fc.
 4. The fusion protein of claim 1, wherein saidIgG1 Fc is at least 95% identical to SEQ ID NO:
 6. 5. The fusion proteinof claim 1, wherein said HJV fragment is a soluble fragment.
 6. Thefusion protein of claim 1, wherein said HJV fragment lacks theC-terminal GPI anchoring domain.
 7. The fusion protein of claim 1,wherein said HJV fragment lacks the N-terminal signal sequence.
 8. Thefusion protein of claim 1, wherein said HJV fragment lacks both theC-terminal GPI anchoring domain and the N-terminal signal sequence. 9.The fusion protein of claim 1, further comprising purification ordetection tag.
 10. The fusion protein of claim 9, wherein thepurification or detection tag is selected from the group consisting ofdetectable proteins, DNA binding domains, gene activation domains,purification tags and secretion signal peptides.
 11. The fusion proteinof claim 1, wherein the first fusion partner is conjugated to said HJVpolypeptide or fragment via a covalent bond.
 12. The fusion protein ofclaim 11, wherein said HJV fragment lacks the N terminal signalsequence.
 13. The fusion protein of claim 1, wherein the HJV polypeptideor fragment thereof is not SEQ ID NO: 62, 63 or
 64. 14. The fusionprotein of claim 1, wherein said fusion protein has enhanced proteolyticstability.
 15. The fusion protein of claim 14, wherein said enhancedproteolytic stability is conferred by a sequence alteration at the aminoacid corresponding to amino acid 172 of isoform A of human HJV.
 16. Thefusion protein of claim 1, wherein said fusion protein has an amino acidsequence with at least 95% identity to the sequence of SEQ ID NO: 10.17. The fusion protein of claim 16, wherein said fusion protein has anamino acid sequence comprising the sequence of SEQ ID NO:
 10. 18. Thefusion protein of claim 16, wherein said fusion protein has an aminoacid sequence consisting of the sequence of SEQ ID NO:
 10. 19. Thefusion protein of claim 1, wherein said fusion protein has an amino acidsequence with at least 95% identity to the sequence of SEQ ID NO:
 7. 20.The fusion protein of claim 19, wherein said fusion protein has an aminoacid sequence comprising the sequence of SEQ ID NO:
 7. 21. The fusionprotein of claim 1, wherein said fusion protein has an amino acidsequence with at least 95% identity to the sequence of SEQ ID NO:
 1. 22.The fusion protein of claim 21, wherein said fusion protein has an aminoacid sequence comprising the sequence of SEQ ID NO:
 1. 23. Apharmaceutical composition comprising the fusion protein of claim 1 anda pharmaceutically acceptable carrier.
 24. The fusion protein of claim1, wherein the second fusion partner comprises a HJV polypeptide orfragment thereof, wherein wherein said polypeptide or fragment thereofhas at least 95% amino acid sequence identity to a portion of the HJVprotein of SEQ ID NOs. 2, 3 or 4 and is at least 50 amino acids inlength fused to a polypeptide comprising an amino acid sequence 95%identical to IgG1 Fc.
 25. The fusion protein of claim 24, wherein thesecond polypeptide or fragment is conjugated to said first fusionpartner via a crosslinker.
 26. The fusion protein of claim 25, whereinthe crosslinker is a DSS crosslinker.
 27. The fusion protein of claim25, wherein wherein the second polypeptide or fragment is conjugated tosaid first fusion partner via one or more disulfide bonds.
 28. Thefusion protein of claim 24, wherein the IgG1 Fc is at least 95%identical to SEQ ID NO:
 6. 29. The fusion protein of claim 1, furthercomprising a BMP-2.
 30. A method for producing the fusion protein ofclaim 1 comprising: (a) introducing into a cell a vector comprising apolynucleotide encoding the fusion protein operably linked to apromoter; and (b) culturing said cell under conditions where saidprotein is expressed.
 31. The method of claim 30, further comprisingpurifying said protein of step (b).
 32. An isolated polynucleotideencoding the fusion protein of claim
 1. 33. A vector comprising thepolynucleotide of claim
 32. 34. The vector of claim 33, wherein thevector is a viral vector.
 35. The vector of claim 34, wherein the viralvector is selected from the group consisting of an adenoviral vector, apoxvirus vector and a lentiviral vector.
 36. The vector of claim 33,wherein the vector comprises a tissue- or cell-type specific promoter isa muscle or liver specific promoter.
 37. A pharmaceutical compositioncomprising the vector of claim 33 and a pharmaceutically acceptablecarrier.
 38. An isolated host cell comprising the vector of claim 33.